Kitchen Table Electronics Repair: Sherwood RX-5502 Multi-Zone Stereo Receiver
Vložit
- čas přidán 7. 09. 2024
- I've been a big fan of the Sherwood RX-410x series of stereo receivers. My own units have proven reliable, but reports of trouble are out there and more frequent than they ought to be. I've wanted to know what goes wrong with these units, so I picked up a broken RX-5502 multi-zone receiver. Its circuitry differs somewhat from the RX-4105 or 4109 series, but the same basic design is used for power and preamplifier circuits.
Sherwood claims a total output power (with all speakers going) rating of some 400 watts. They are dreaming!
As found, this receiver would just shut down a few seconds after being powered up, followed by a blinking standby LED. Normally this indicates a power amplifier or power transistor fault, yet I did not think such a fault existed here. Watch and see how I did some troubleshooting and arrived at the cause of the problem. I'm not sure it's totally fixed yet, as the new regulator seems to be running awfully hot. I'll have to look into that some more, but it did survive running for several hours tonight.
Now all I have to do is find some screws to replace the ones I didn't get with the unit and straighten out the cover a little bit.
There are some interesting features that were never realized in this unit. When sold as a TEAC AG-980, this unit gains an optional serial port and some other connections. Sherwood's designer clearly thought about adding support to connect an iPod and support for DAB broadcast decoding. (You can see this in the video.) Outside of the things populated in the TEAC AG-980, I have no idea if these other artifacts were used. There is also the header for an optional RDS board, which I really want to find...
Some Sherwood receivers have a self-test mode that can be helpful. This test usually just clears the memory, displays the firmware revision or illuminates every character in the display for a few seconds before shutting down. In this receiver, the display test remains on until the set is shut off, which came in handy while troubleshooting the power supply. To access the self test on an RX-5502, make sure the main power switch is on. Press and hold T/P Mode while pressing the "On/Standby" switch. The display will read "CLEARED". Immediately press the MEMORY to run the display test or show the firmware revision. (Note that this is not documented anywhere...I found it on my Insignia NS-R2000 first simply by pressing buttons. Not all of my receivers have it...my RX-4109 does not, while this and the RX-4105 do.)
I am going to buy a Sherwood Rx-5502 today for 25$ from Gumtree market. I was looking for a simple amplifier with less circuit and features to avoid complications. Your video reinforced my plans to go for it. Thanks again for the great video.
shhhhh, don't tell anyone else that the Best Buy Insignia 2 channel receiver is in fact a pretty good quality "Sherwood receiver". I just bought one and i love it! My vintage NAD set up is just too darn heavey for the really nice all pine component rack i assembled. Great video, its really inspiring. Most people are so quick to through equipment away instead of servicing it. Look at a similarly priced Sony and even Yamaha at 50 dollars higher which come with spring loaded speaker terminals.
I love how you talk all of your troubleshooting thoughts out loud. I am greatful.
Nice work Bud , ELO from my Hometown Brum UK . I have put 2 fans in my old Pioneer , a micro fan blowing on the back of the heatsink and a 4 inch drawing hot air up and out Very reliable
ATB
Another "Like" for this video. These are "don't forget" lessons for me, even 20 years after taking my electyronics class. Thanks for making them.
I used to work in a TV repair shop and the owner would take anything and everything in for repair...if he could make a dollar fixing something he'd take it in. It was a fun place to work and I got to learn how to fix all kinds of crazy stuff.
Bill I have a Sherwood RD 7405HDR. This is the rare unit that has the HD radio tuner. It sounds nice and bright with good highs unlike their other receivers. I dont have any issues since it's new in the box. (New old stock) I just wanted to share that. Thanks for your videos and your explanations
if you doubt a regulator, it's better to test it outside the circuit - their datasheets usually have test circuits which are very easy to built.
In such cases, it's possible that the capacitors in front or behind the regulator are shorted or have high resistance, and may un-short/conduct power well enough once they heat up a bit - so at cold start, the heatsinks around are cold, won't start As heatsink go warm, cap goes warm, lets regulator work
Sometimes you can use hair dryer to test this.
Theese receivers sound great, I had one back in the day, and it still works to this day in my friends house.
Bill I like the way you fix those stereos. I actually have a sherwood 7405 HDR which has HD Radio. Sounds awesome
Top marks Bill...I think you are fast becoming my favourite CZcamsr!
Considering you are self taught, you could run rings round people classed as 'Professionals' in this field!
I thoroughly enjoyed the BlogTV show the other night! Thank You!
I still can't get over the 'Outstanding High Quality' of your audio and 'Perfectly' in sync video!
You really are an Amazingly talented guy! :)
Thanks for another stereo repair video. Maxxarcade, and you... I always love your repair videos.. esp if they have to do with amplifiers, or receivers.
I had a RX-4109 receiver once and it would not even run the standby. Then I got a RX-4105 unit from our transfer station, I thought I give them one more chance. It works great, the other one likely had a power surge or someone was not too kind to it!
Hi uxwbill, finally got it up and running, it was the micro controller was the problem. thanks for all your help.
Hey Bill...I have a solution to those crazy connectors...I always keep a set of magic markers. I mark each connector as I unplug them. Just mark them each one with a different color red, green, blue etc.
I would have looked into upgrading the regulators to something a little better if available. If not, use original replacement parts only and increase the heatsink size on both to prevent this failure from recurring.
Wow! How I wish I saw this earlier, as I just assumed the outputs crashed on my similar/identical and cheap Insignia Receiver. I replaced them- Hey they're a buck a piece, well still protect mode. Next the caps...OK. I ended up here. Unlike the Sherwood, Insignia does NOT use a heat sink! FYI- I would take the 4109 over a NAD 3020 anyday. Likely as those too, were once considered budget throw away amplifiers. Plus, the 4109 sounds as sweet if not better! What advantage the 4109 has over the Insignia is a removable phono amp, which I have retrofitted into stand alone units.
I have a sherwood some where in my attic unsure of what model but I remember one thing that was different than most of the systems I have worked on It has 4 ohm speaker connection on 4 channels most of the sherwoods I have seen and worked on over the years were 8 ohm I have seen 2 ohm systems over seas when I was in the NAVY.
I have tinkered with it all that I want to for now....you reach a point when you look at an $89 receiver and ask yourself "how much is my time worth?". If you have a use for it and the shipping doesn't cost too much, its yours for the asking.
@uxwbill Hi Bill, thanks for responding. I actually didn't think about that, I might try it out. The 7805 gets its voltage from a bridge rectifier, which sends its respective voltage through a capacitor to filter out any hum.
Despite the errors I found this video very helpful, thanks.
I got the same multimeter. Cheap, but it works. One of these days I have to pull one of my troublesome amps (Sony STR-434) on the bench and fix it. I get random static on the outputs and sometimes the output clicks off and on again (over current protection?).
Hello uxwbill I have ridgid stereo with out power. I found the fuse blow out, the fuse for it is T630mal 250 v. I use F500ma 250 v just to tray and ones i plug it the fuse blow out. that because the fuse is no right or it may have other problem? please help..
Now, what are receivers used for? Just a way to hook speakers up to many pieces of audio equipment? I only have a vintage CD player from the 80s, but I have it hooked up to my TV to get sound. Works great that way!
@uxwbill I managed to find a service manual. I'm going to do some voltage testing on the power amp board. DC bias tests are a bit weird on the right channel, floats between 15-55mV, while the left channel is steady at 13mV. Nothing obviously bad inside (no visible leaking caps or burned stuff), I seemed to recall this unit being sensitive to humidity, so there might be some marginal working parts in there somewhere.
is that a Rx-5502 service manual ? Do you have a link for it please?
My RX-4109 had an open primary of the mains transformer. There is a thermal fuse hidden in the primary.
Thanks. I'm starting to look at that thing as my new hobby instead of my amplifier, so I'll probably keep snooping with your suggestions, but also go buy a new amp!
The amp needs to be fully powered up to get a sensible reading from the regulator, in your case you have only a few seconds to get this before the amp goes back to standby.
You indicated you wanted a Sherwood 4109 that didn't work. I have one that works and one that doesn't. You can have the one that doesn't if you tell me what went wrong so that when the one that works goes bad, I might be able to fix it. Tested the voltage regulator 7815 and its working. Otherwise the same problem everyone else has, powers up then powers down.
now I noticed you have a lot of room in there were if those heat sinks are just not big enought you could replace them with bigger ones for better heat disapation. I used to have and old audio amp like that were that happed I replaced both the regulator and put a larger heat sink on it and also added a nother board I build that had a tempture sinsior on it and added a cooling fan to it so when it got ware it kick on and keep it cool.
i almost bought one but instead bought a $110 Teac AG790 because of the slightly better reviews it was a little more expensive but it is serving me well i did not know about the c/d speaker sets on the sherwood though that is neat
I went to my local Radio Shack and they sell these for $99.00...I think I'll buy one.
I was able to pick up an rx-5502 as well, but I apparently just have bad luck.
The primary on the power transformer is wide open. The unit still has standby power and will have the red led indicator come on when you engage the front power switch. The dc relay will also click once you toggle the power button... however there is no front display and no other activity from the unit.
Can't find the transformer or anyone currently selling another bum unit so I'm gonna part this one.
@uxwbill Yes. I have a video of the repair here on youtube. Power spike "killed" the transformer (not speaker load) and protection fuse on the main board was intact. Measured open primary and was about to toss the receiver as that critical part (mains transformer) was not available as a replacement part.
Found the SECRET HIDDEN defective thermal fuse and aborted it.
Receiver is alive again, powering our 2nd floor laboratory JBL ceiling speaker system with much greatness. No overheat.
Thanks for the great repair videos, please do more.
Will this model work with 4 kicker speakers kb6000? Each of the speakers is 75watts RMS 8 ohms each. I would just want to play off of one source at a time. I was thinking about plugging in one pair of speakers to (A) and the second pair to (B) and just play off one source. is that possible? Anything else I should know
thank you. ok so hooking up 4 8ohm speakers, will result in lower ohm from receiver....I was hoping to get the 75 watts rms to each of the 4 speakers at 8 ohms each.
Love the video as always, made me fall off my computer chair when you sed about not useing headphones at the end and smokeing your brane and ears!!! Keep them comeing hope your ok . Phil ;-)
Hey Bill,
I just ran across your channel recently and subbed. Really enjoy your vids.
great going. Still gotta fix my STA-2000 reciever. One of the guys i know in town said it sounded like a power transformer gone bad
Bill have you ever seen a Sherwood tuner? My neighbor tossed out a Sherwood TD7010R tuner.
it's in very nice condition , almost looks new. I plugged it in and it has display. Don't have an amp to connect it so it's not tested.
HI,I HAVE SHERWOOD 1409 STEREO RECEIVER,POWER DOS NOT STAY ON SHUTS OFF AFTER 4,5 SECONDS,DO YOU KNOW WHAT'SIS THE PROBLEM,THANK YOU
@uxwbill I'll do as you say, so any way i do have to wait for the fuses i ordered. thank you and I will let you know how it goes.
uxwbill, i have one of these RX-5502 receivers and after turning main power on the small light led shows up, then after pressing standby power the unit goes dead immediately and the light turns off..i do hear a click at the relay inside...i have under 1 volt at any of the power points and grounds at ribbon cables....under half volt at all power transistors....the fuse is not blown....how do i check the large main power supply and is there a thermal fuse on it and where?? Thanks for the help.
I repaired a denon Avr-986 one of the 15+- regulators for the op amps was not working. the outputs was fine.
God, that Sherwood looks like it is built very similarly to the Pioneer VSX-820-K I just repaired. The bottom case looks identical.
That would make sense then! Did not know that.
Im just curious about the 12v regulator that shows only a few mV when standby light is blinking. When the device did start up occasionally.. did you check the regulator and there was only a few mV even then?
I have a broken Optimus 3680. It started buzzing really loud and one channel stopped working. I unplugged it for a while and the buzzing stopped for now, but when I pan over to the "dead" channel, it has a very low volume. I think the source of the buzzing is all of the inputs are being amplified at the same time. I was moving the source to different inputs while it was on but didn't switch the input on the receiver and it still gave a signal, however buzzing. Does this sound repairable?
I've found the circuit boards on these barely use any copper and hate heat!
@uxwbill I will talk to my brother about that, he might be able to help me get it sorted. There is not obvious battery door that I've seen. Basically, it's a big black unit with some buttons on the front and a volume knob. I've not looked inside it all that much though. Thanks for the help :)
I checked the speakers with another receiver that i have and they are working fine.
When i opened the amp i noticed that it had a fuse so i checked the fuse and it is good. The amp powers on without a problem.
At the time i was using the amp to run my turntable and i had the receiver off.
Tahnk you much for your suggestions, maybe i need to turn the receiver on, but the rca cable connections go to the amp.
Hope this makes sense.
Thanks for the effort, I hope you don't mind me pointing out a couple of errors. You say the voltage is very low on the +12V which makes you think there is something wrong with the 7912 regulator, the problem is the 7912 is a negative regulator, you should be looking for the -12V to test this, not the +12V. Also I didn't notice you saying anything about the state of the amp while you were testing this because in standby mode you will get a very low voltage reading out of the regulator
I have an Insignia NS-R2000 are you familiar with this model? I am able to get a standby light to come after powering up and then once I select an input (Aux, Radio etc) this light turns off and Speaker A and Speaker B light up. This normally happens in sequence with the name of the input I selected also being displayed on the monitor. I've removed the cover and air dusted it a few times but I am not very tech savvy when it comes to this sort of thing. Any help or advice would be appreciated
excellent repair :-) , i would fit a larger heatsink to both 78 series or see if an input resistor is possible to lower the dissipation to a safe level.
Companys allways cut costs and bypass the designers carefull design, shame.
he bill a quick question i have a pioneer reciever with slide pot and has 100k style how do i know what to get for replace and where can i get them
the sherwood is 89.99 at local radio shack by the way
Sounds like my problem gonna try it right now thanks.
The proper way to troubleshoot this kind of thing is to do some tests. Otherwise, you're just guessing, and probably spending money on things that won't be the problem. A good place to start? Check the regulator's output pin and see what's there.
You certainly know your stuff there. I have a harmon Kardon Reciever which loses it's settings after power outage, it did not do this in the past. Is there any thing from this information that you can tell me as a rough guide. It's an AVR4000, got it second hand, sounds great, runs fine. . .now but I have to retune the radio every time I turn it on.
Thank you for replay the massage, I do have a multimeter is there some parts i can test for continuity or ohms? and thank for the advice.
Hi Bill,
I have a Sherwood RD6506 AV receiver - it does exactly the same thing as the amp in this video, shutting off a few seconds after being powered on.
I have some basic knowledge of electrics circuits, and own a cheap multimeter. What would you suggest would be the first thing to check? Any help would be appreciated.
I got a KENWOOD amp... It's a great amp. Problem is.... I can't get it off of "Tuner" mode. Infact, none of the buttons do anything, except the volume up/down. If I press for example video 1 it will not change channelsi the same obviously is true for aux, video2, phono, etc.
It's a bummer because I got the amp at a charity suction with a "WORKS" post it note on it. I opened it up and despite the outer area being immaculate, the inside was absolutely COVERED in dust. So I dusted it (very very carefully I might ad) I also cleaned out the headphones jack. -no change.
Any ideas?
Best guess is that you have a stuck button, damaged circuit board traces/keyboard matrix or confused microcontroller.
does it buzz with inputs disconnected? Lets see if its the amp or the source
@uxwbill sounds like a good idea :-), if they are too big then look at the old heatsinks on processors.
I would say to mount a cpu fan above the 78 series but it may induce noise into the unit :-(
Where can I get a 4105 schematic, I need to re-bias output after replacing right side output transistors, I don't see a pot for biasing, they must have used a fixed bias servo!! Any info would be helpful!!
A well directed web search with a reputable search engine will find it. Try using the RX-4109 model instead, they're both covered by the same manual.
ELO Strange Magic. Classic Tune.
hello i have some capacitors that need replaced they read nichicon ce 85 c 10000 u f 71 wv lk m
any idea what they are and where i could get them they are out of a sony reciever any ideas you help would be greatly appriciated
there is only 1 fuse in the pioneer,,,,,,,,,,,and it is good,,,,,,,,,,,,thought it was the relay switch,,,,,,,as pioneer cliks 2 times before it turns on.! help me Bill...?
would putting a small 12v fan on the 2 regulators heatsinks help them with longer life?
Yes.
Bill, help me. I have the same problem. BUT I have measured the voltage in the pin you did it on 10:32 and it shows 12v. Also I have measured the voltage on each of the voltage regulators 7812, it shows output 11.9-12v for each of them, and the near VR 7912 shows 11.6v. I think it is good, isnt it? BUT SHIT, IT STILL SHUTS OFF AFTER 2-3 SECOND AFTER TURNING ON!!! Any ideas?
my sherwood stoped working as i whent to sell it indacaters move but no sound worked no mono only befor that a while
Dont worry i wanted to subscribe, Your videos are very informative.
I already did that and of course the the power cord was disconected.
If the problem is beyond my expertise i will take it to a qualified shop.
But i am debating if it is worth it some of these models from the 80's where not the best quality.
Nice work! That sherwood sounds great.
I will take it to a shop and see if it's with in my budget to get it fixed.
I started building a VFD clock a few months ago which uses a 230VAC to 24VDC transformer for the VFD, and also a 7805 voltage regulator for the microcontroller. The microcontroller doesn't need much juice, maybe just about 10 mA. Although there is almost no load on the 7805, it gets boiling hot, so I figured, that it's burning away the remaining 19 volts as heat. I'm still trying to find a solution to cut the waste. The current state can be seen here: watch?v=5QzI2qikEak
Do you have any ideas?
My RX 5502 just started making a loud pop when I turn it on but no music from the speakers. Now it isn't popping but it isn't playing either. I can hear a relay or something clicking when I turn it off and on. Is this repairable or should I scrap it and head for BestBuy?
I haven't opened my 4105 yet but it started doing this quite some time ago so i would just leave it on , because at times I could get it to stay on. I'm curious do the 2 regulators you're checking have power to them as soon as the unit is plugged in? I figure they must because you have your unit plugged in but it isn't powered on, but I then thought maybe I'm missing something? My repair expertise is somewhat limited as if I have a service manual or instruction (like this video) I'm able to do repair work, but to just open something up and attempt repair I would have a difficult time , unless it was something obvious. I've got an old RCA dimensia amp I'm hoping to use while my sherwood is down.
hello there I too love these units but don't seem to find them as much any longer, I have purchased about 6 of these type sherwoods I have 2 yet that keep shutting off I am a novice but eager to learn, that's why I didn't throw them away, I play guitar and man do 2 of these units really crank out some sound. my question is I think the lcd is burnt out and shuts off the rely any help would be appreciated.
As always Bill, awesomevid, thank you very much,very entertaining!!!
Bill must be the main power supply I used 1 set of speakers for 2 amps,,,,,,,,and I forgot to take the plugs out when I turned on the pioneer ! Some resistance must have passed through the pioneer,,,,,,,,,? Mind you the second receiver was turned off,,,,,,,,,,,,,when I turned on the pioneer,! It just cliked the pioneer,! Now it is complete dead,! wont turn on fuse in the pioneer did not catch it,! shawn! I bought it sealed box with no warranty
My 4105 has a very annoying high frequency hiss ~ the 240hz zone through all the channels (even with no inputs). I replaced the power supply filter caps and the speaker wires. The hiss is still there, though slightly less obtrusive. Listening through the speakers at a reasonable level & distance, the hiss is a little too present. Have you noticed a high level of noise with your Sherwoods? Any suggestions?
I Made The Mistake Of Buying A Sherwood RX-4109 At A Yard Sale Without Asking To Test It Right There And I Got It Home And All It Does Is Turn On And Turn Right Back Off, Is It Garbage?
I Wouldn't Mind Trying To Fix It But I Know Nothing About How To Find Where The Problem Is So Instead Of Messing With It I Have It Tucked Away In My Closet
Not dogging you or your video, it was great. I would advise anybody looking at the Sherwood RX of any kind to stay away. These things are bad. I've worked on three of them with various problems and seen others on youtube with various different problems. The first one was a open transformer. A wire broke off inside. The second one was the small transformer for standby was smoked. The third was user damage, a shorted output transistor. One thing about them as far as performance I don't like. [Don't think they have enough bottom end], bass but that's just opinion..
I'll be among the first to say that Sherwood's quality control is a bit hit or miss. All I've mine -- including a few that I bought broken and found to have no problem at all, or whose problems were conclusively caused by user error -- have been good to me.
Speaker choice makes a big difference with the RX series receivers. And maybe that's been true for a while now: the receiver attached to one of my computers is a Sherwood RA-1140 from the 1980s. It sounds very similar to the modern RX-series and speaker selection makes a huge difference there too. In addition to being the smallest receiver I've seen with a discrete output stage, the little RA-1140 is a personal favorite. Lots of receivers can blow it away in terms of power. None have in terms of sound quality -- I've swapped it out for others, and time after time it comes back.
i had a sherwood for 4 years and one day it just died
so i pulled out my Kenwood thats from 2002
I'm pretty sure those speakers you had at the end are the exact same Sony ones I have on my desk, not bad speakers actually, use them as PC speakers.
Hi Bill I have a Sherwood RX-4103 and it was working just fine and now sound like a cheap radio. No base at all.
What do you think happened?
I don't know with any certainty what may have happened. I'd test your speakers with another receiver -- perhaps the RX-4103 started feeding DC voltage to the speakers and burned out the woofers. If the speakers are OK, I'd go over all the operating controls and make sure nobody set them to absurd values.
Also check your speaker wires.
I have a Sherwood rx4109 and it’s turning on and then seconds later shuts off... I’m not good with electronics what do you recommend
I hear one relay click and then it shuts down with a solid red light above power button
Mine I plugged and now it just shuts off seconds after turning it on and I don’t know what’s going on and or haw to fix it
If yours is brand new, you should simply exchange it for another. Likewise, if it's under warranty, contact Sherwood and let them take care of it. If not, you'll have to do some troubleshooting to figure out where the problem is. Check your speakers and speaker wiring for any shorts. If that doesn't turn anything up, you will at a minimum need a multimeter and a basic understanding of electronics theory and class AB amplifier design.
Hey Bill, with all zones on, is i it still putting out an 8 ohm load???
forgot to mention the model of my Sansui Amp.
It is an A-1110 amplifier.
advice you can give me.
Best regards
Can you tell any difference in the bass response between the RX-410x and this receiver?I noticed Sherwood shows a different frequency response for this receiver compared the RX-410x.Sherwood filters the low end out on most of their receivers.nothing below 40 hz is passed through.it makes my speakers sound hollow without that deep bass.
Good song to play since it's working!
good job uxwbill but that is the oddest looking kitchen table I seen..almost looks like a bed btw what model is the kitchen table your using?..lol I am kiddin around
In looking at reviews for various receivers, I came across the following review of the RX-5502. The reviewer seems even more enthusiastic about this particular Sherwood model that even you are. In your opinion, would you say this review is accurate or a lot of exaggeration?
"by p51joe
Sep 28, 2019
Sherwood RX5502
SUPERIOR TO MOST MODERN ERA RECEIVERS
First off, if you are looking for a 2 channel receiver with decent output for most situations, this is it. The amplifier is of a tried and true design having it's roots in older equipment like the NAD 3020, only using faster and more powerful output transistors. Here is where this receiver shines. It had a dedicated and discrete phono section operating on 15volts. Frankly, If I could buy these cheap enough I would buy all I could get my hands on and sell the phono amp as a stand alone with a power supply of my own design! Anyway, the only fault to find and frankly typical of MOST electronics made today is the voltage regulator pair. If left on continuously for weeks on end, one of the pair will burn up due to no heat sink. But you want to know how this sounds. I have audio equipment costing thousands. (Marantz 7 and Model 9's) This little unit sounds better than most any receiver I have auditioned, including 1970's Marantz units that people pay stoopid money for because they have pretty face-plates. I would recommend this unit over a Cambridge Audio, Yamaha or HK receivers made today and frankly any other Sherwood with the exception of the S-7900A/8900A and S-7310. This unit shares architecture with Insignia and Pioneer, as all receivers come from the same spot on the globe. The difference is that Sherwood has some subtle changes to the circuitry that make it sound fantastic! The take away is that if you listen to records, you can NOT beat this thing for the price they bring used. You can not beat it's sonic performance even if you spent $500 on a receiver."
I'd say it's an exaggeration. The Sherwood's not a bad receiver for what it is, but it's not THAT good.
@@uxwbill Shit, and I just bought one on the strength of this guy's review. I already have an ONKYO TX-8140 which I was going to swap out for the Sherwood RX5502. I guess you would advise me to forego this change then?
Bill- You inspired me to buy a desoldering iron and replace both 7812 voltage regulators, hoping it would be similar to the problem you had on yours (my RX5502 dies after 10sec just as you describe). Wish I could say it started playing ELO when I started it up, but it just clicked off after 10sec again to remind me I am a mechanical engineer, not electrical. I am down but not out, and looking for a next suggestion? Thanks!
Hey great work by the way very informative and with great sounding knowledge. I have a simular issue but mine the Std By light stays on and I have .3v at both the input sides of the volt rgs! and I have .3v at the amp circuit board connection and not 12v like you. Do you know where the 25v or so comes from for the VREG x2?? Cheers.
All of the voltages come off of the power transformer's secondary winding as AC, are converted to DC by a bridge rectifier (diodes), filtered through capacitors and then go directly to the various regulators. I suspect a broken trace or blown fuse/circuit protector may be part of the problem, as an overload sufficient to pull the 25VDC supply down to 0.3VDC ought to make something start smoking or blow up outright.
@@uxwbill Thanks for your reply and extra info much appreciated. The board looks fine with no obvious burn marks, tracks broken etc and I have 14VAC on both red wires to yellow center wires from the output of transformer. What voltage should be at the output of the transformer 25Vdc? if this is the case then I think may be the transformer could be suspect? The Amp has been running full 4 channels with 8ohm speakers not 16ohm like recommended!, which would also mean that it was drawing a lot more power yes? Also I'm in Australia and the power is 240Vac just for your info. Cheers.
@@uxwbill very nice job !! I have found very nice condition Sherwood Rx 4030r. Do you recommend this model ?
i had an old stereo unit that would just turn on and off all by itself it wouldnt stay on or off could never figure out the problem
great song, whats is called again?
Hey uxwbill.
I have a Kenwood KR-V5580 which will not come out of the standby mode when I try to power it on. Do you know of anything that could cause that problem? Do you know of any way for me to be able to help fix that problem? Thank you! :)
I have an old sherwood hi fi system with a faulty finish sticky black are there any fixes
None that I know. If it's rubberized plastic, that stuff is known to turn tacky after a while. Baby powder will fix it for a while.
uxwbill. I have a similar problem with a RX-4109 and need your expertise. If you are still there after almost 9 years and willing to hear me out, I'll take the time to explain what I have going on with my son-in-laws receiver. I thought you did a great job with this video. I'll check back later.
You can certainly describe your problem here if you'd like. Depending upon your skill level and equipment, I'd start with some basic checks. For example: do you have voltage from every output of the transformer? Is there voltage reaching and leaving each regulator? Have you checked the output devices for shorts?
I have a basic understanding of power supplies. I know nothing about receivers. The issue is, turn it on and it shuts down about 5 seconds later. There is one 9 volt relay that energizes while on. If I unplug the transformer's secondary wires from the board, the receiver will stay on. In fact, another relay will energize. The voltages of the wires I'm unplugging is around 85 volts. There is a center tap, measures 42.5 volts as expected. I found two regulators. A 5 volt and a 15 volt. Both are working properly. I don't see anything burnt and there are no overheating smells. That is as far as I've gone.
Check all the power and driver transistors in the amplifier. It's likely one or more are shorted.
There are 6 transistors mounted to a large sharing heat sink. Checking collector to emitter, they all seem to check OK. I did notice wire traces on the main board labeled +15 and another -15. I only measured -3 volts at the -15 line. The +15 measures correctly. I'm not sure where the -15 is suppose to come from. I'm beginning to think I may have to remove the board and try to follow where that secondary transformer circuitry goes. This is the one when I unplug it, the unit does not kick out.
At one time I knew where the -15 V came from, but I've forgotten. I'll have to check some of my notes, assuming I can find them. I think I might have had some correspondence with someone who also saw a deficient -15 V supply in theirs.
uxwbill, I have the same receiver with the same symptoms. I pulled the cover off and checked the voltage output (as you described) from the regulators and they are reading 12 volts. Do you have any other suggestions?
Hi there uxbill,
very good video, very informative..
I have an 80's Sansui amplifier that was working fine and then it quit.
it has power but does not provide sound to the speakers, could you give me an idea of what might be the problem.
I sprayed electrical contact cleaner to everything but not change.
Thank you
Hi uxwbill, ok i replaced both 7812 voltage regulator and still turns off when i press the power button but i don't get a blinking red light it stays solid red. when i turn on the power i have the volt meter on the connector i get 12.34 volts then it starts to drop and i hear a relay on board turn off. also the amplifier is out of the unit. what voltage should read on the other voltage regulator 7912? hoping to get this up and running. just over two years old. thanks for your help.
The only advice I can offer is that of continued troubleshooting. Something's loading down your 7812 regulator (or its power supply is bad), and you'll have to find whatever that may be. Look at all the passive components around the 7812 regulators. Remove them, and test them.
The 7912 is a *negative* voltage regulator, and should have approximately -12 volts DC on its output. As far as I know, it is used only for the phono preamplifier.