stereo buss troubleshooting - headphones, master fader & line out | Tascam 244
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- čas přidán 5. 12. 2019
- I had a Tascam 244 in the workshop with an issue where one side of the stereo image was dead, both when monitoring using the line out RCA socket son the rear of the unit and when using the headphone sockets at the front of the unit.
In the end it turned out that the unit had two separate issues with overlapping symptoms 1) dry joints on one side of the stereo amplifier and 2) a dead operational amplifier on the headphone output.... but before I could diagnose those problems I had to first establish that the fault did not lie with the master fader or other components in the stereo signal path, so this video also includes a demonstration of how to remove the back panel and meter PCB form a 244, and use of inexpensive op amp and component testers.
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Thanks for all these vids . I will get round to fixing mine next year as I still have dozens of demo tracks to digitise one day. Love my 244
I must compliment you for your work about the 244, it's a complex machine and your videos patiently and accurately illustrate how to deal with the various problems.
I fixed a Porta 07 from what appears to be a common problem, polarity inversion. If you think it's useful, I can share my findings somewhere.
Thanks, please do...I actually have a porta 07 with that issue, I assume there is some dead semiconductor near the DC input socket? (I haven't got round to troubleshooting it yet)
@@Tetrakan Yes, more or less. The first thing I noticed was the power mute circuit had a transistor visibly burned, a 2SC1815GR (near the DC input socket on the right side looking from the back).
That circuit is similar if not identical to that of the Porta One or the 414 MK II.
As suggested by SkywaveTDR in the Tascam forum, I replaced it with a C1845 of similar characteristics, I chose one with 290 hFE.
I was lucky because the nearby Zener diode usually goes away as well, it's a RD12EL2, mine was OK.
Differently from the other two models the 9V regulation is not achieved with a 317 or a 7809 but with a M5237L in a slightly more sophisticated manner.
In the M5237L datasheet there are two example application circuits, the Porta 07 works in a similar fashion.
The M5237L only drives a power transistor a B901 (an 2SB1314 in the datasheet's examples) which holds all the load.
This is the large transistor mechanically connected to the transport mechanism in order to cool it.
It looked perfectly fine in my case but since I hadn't a working 9V (I measured about 3,5V) it was the prime suspect.
To test the hypothesis I used an A614 Y-821, with the following precautions.
First the pin out is reversed, it must therefore be mounted inverted.
It can sustain about half the current so I didn't connect the mixer side of the Porta, nor the transport mechanism because (third) the A614 cooling fin it is not electrically isolated like in the B901.
It worked, I measured a steady 8,98V.
The final step was to find a suitable replacement ( I don't think that in this case the hFE is important), I opted for a 2SB1370. More powerful, insulated fin but again reversed pin out.
But I didn't have the patience to order something so I placed a new dissipation plate in front of it and fixed to the transport with a longer screw.
The next electronic order I'll take something better. :)
@@Gezira excellent, thank you, I will refer to this when I get to my own porta 07
@@Tetrakan You are welcome, if you need more details please ask, I will try to do my best.
Ive got the same 244 but the left channel is quieter than the right. It’s not completely dead though, is there a calibration I can do to adjust the balance without replacing anything or having to resolder any components? Thank you, love your videos they’re extremely helpful!
Your videos really been helping me understand the tascam 244 do you have any video showing whet it hooks up to I have been looking but no luck
Thanks. I did a series of videos where I tracked a song on that model, hooked it up to various pedals, mics, instruments etc, here's the third in that series, get back to me if this isn't what you meant? czcams.com/video/gJFhiO5P_kE/video.html
First off, you're doing an awesome job! Since it seems that these recorders are probably not going to be manufactured never again, it is very cool for you take the time to share your knowledge. I've managed to hoard a few non operating 4 and 8 track recorders and might even be able to fix some of them after watching your videos,
Secondly, talking about master faders.. my 244 has a faulty one (seems like the part connecting the pin to the carbon track got corroded somehow) would you happen to know where to order a fitting replacement? Shouldn't be all that hard to find since the pins don't have to match any pcb holes but still, it would save time and effort if you could provide a link to one or even just a brand/model that is sold at the moment.
Thanks. I'm sorry I don't know where to get replacements, I've always relied on buying 3, fixing 2 and keeping the worst one back as a parts donor for future projects. As a workaround might you bypass the master fader altogether with jumper wires? OR use a dual pot or pair of pots, and mount those on the lower case?
Thanks for your videos! I just got a 244 and i'm still trying to learn how it works from the user manual and these videos. Total beginner to the whole area of tape recording. So far i didnt fully understand the buss system and i'm not sure if i've bought a faulty unit. I cant get channel 2 and 4 to record on the tape. I get a monitoring signal when they are panned to the left but as soon as i turn the pan to the right the signal vanishes from the VU and i cant hear anything. If i use the 4 tracks at once setting all tracks do record. Any ideas what the problem might be and how to fix it?
I'm wondering if it's a fault with one side of your master fader...if you play back a prerecorded cassette in remix mode are you getting output from both sides of your headphones and/or line out?
@@Tetrakan Thanks for the quick answer! The right side is really quiet and sounds distorted
You're probably going to need to access and pry open the master fader to see if it's full of lint or maybe one if the brushes is corroded. If it looks okay and checks out with a meter other possibility is the master faders are preceded and followed by opamps, they can go bad and if they do much louder or quieter signal plus distortion are common symptoms. They aren't expensive but they're a bitch to access...I mean you'll learn a lot tackling this yourself but it will be daunting!
Thanks so much. I’ve traced down my dead right headphone channel to a bad op amp. Been googling every which way but can’t seem to figure out, what is a modern op amp should I could replace it with?
Never mind found the parts manifest in the service manual. NJM386D it is!
Great, they're still available I think, or at least affordable NOS I think....
I have a Portaone, No Right Channel audio from headphone or line out. I cant find out where the L/R split in the schematics, Im new to reading schematics though. Would you be able to help and take a quick look and let me know what section to focus on? I was hoping it would be similar internals!
Hey I've got loads on at the moment but I'll try to get round to giving you a better reply....meantime can you let me know if you are having the issue in remix mode or cue mode or both?
Thanks for the reply! I found that the master fader itself wasn't sending any L audio, so I just patched it always on full volume from the back. works a charm. If you'd reccomend a different solution plese let me know. I did reflow all the connectors for the fader
@@Jamieip Its a good thing that you have narrowed it down to the fader. You could try desoldering the fader, prying it apart to clean and reinstalling. So long as the little copper brushes haven't actually snapped off or the conductive plate hasn't corroded so badly that it no longer has electrical continuity, this should work, its just fiddly, good luck.
@@Tetrakan thank you! the mixer PCB is a pain in the arse to re install so im happy with it maxed out for now! Ill get to it one day!
@@Jamieip Hello please can you describe me precisely how you did bypass the master fader ? There are 6 pins on my 244, i just made as i could see in the @tetrakan video , pin 1and 2 shorten together, same for 3 with 4 (ground) and 5 with 6 ... Is this what you did ? When i do this, i only get minimal volume on both channels, not maximum. Thanks for your help
Hello @tetrakan I' would like to bypass master fader for testing, when doing the 3 dupont wires loops (pin 1-2 , pin 3-' (ground) and pin 5-6 .. I only get the minimum output level, not the maxone, is there something to do more ?Thanks for your help and your wonderful videos
@Tetrakan : Hello and sorry to bother you again. i come back after further testings, trying to get the Right Channel (Buss R) to work.
In REMIX mode, I get a very very low sound on right side of headphones and line out. Same in Record mode, recording to buss R (track 2 or 4) is very very low ,
When I try to bypass the MASTER FADER (using female Dupont Wire as shown in the video), It seems to make BUSS R to work, but it looks as the MAster FADER isn't maxed out, it's just at a very low level, for LEFT and right side.. So I can't understand how to "max out" Master Fader before bypassing it.
Am I missing something ? Fry open the MAster Fader looks like a hard job and I'm afraid of missing something important before doing it following your other video. Thanks a lot for your help or the help of anybody that did follow your path :)
@@francoisesco3606 Hi, if you bypass the master fader, the signal on both sides (Left and right) should be at maximum. This is because the master fader is a passive component, and it can only attenuate (turn down) the signal. Bypassing the master fader asks a question "Is the volume problem I am having with my stereo signal level being caused by the fader? Or does the cause of my problem lie somewhere else?" If you get a maximum level in left and right, you know the fader is the cause of the issue. But if one or both sides of the stereo image is quiet, you know the level problem lies elsewhere, either with the signal path immediately before the fader, or with the signal path immediately after the master fader. I was not a "fly on the wall" watching you bypass the fader, but assuming you have done it correctly, you still have a quiet R channel, even with the fader bypassed, correct? From that I owuold conclude the fader is not causing the quiet right channel. SO then there would be two possibilities. There are some capacitors an opamp and connections between the pan control and the master fader, maybe one of those failed? Or, there is a similar group of capacitors an opamp etc after the fader, perhaps the fault lies there. If you were curious and wanted practice, you could use an audio probe to find out which of these two parts of the signal path has the problem. but because the parts are cheap and fungible, I would be tempted to just replace both opamp chips, all 8 capacitors, and retouch the solder.
@@Tetrakan that exactly the big question ! I must have make a mistake when bypassing, or my Dupont Cable doesn't fit good ? .... First of all I precise that problem stay the same during tape playback or monitoring an input.
I try a description :
- Normal use : Master Fader plugged on its connector... I get full volume on LEFT and very low volume on RIGHT. A big difference that I can't fully compensate on my mixing console.
- When bypassing the Master Fader :
"Dupont-jump" pin 1 with 2 , pin 3 with 4 and pin 5 with 6 ( similar as in your video, starting pin 1 from the left when in front of the connector)
The volume is now very quiet but EQUAL ON BOTH LEFT AND RIGHT Channels ! So the right Side outputs at the same quiet level as the left, could be a proof that the master fader is the issue.
I get equal volume on RIGHT and LEFT but the volume is now very low ( got to give about +30 db I gain on mixing console, lots of noise of course ) ...
Here's why I assume a wrong bypass of master fader : If I take back the 3 Dupont cables, and don't replug the master fader connector, the volume stays at the minimum, the same as with the Dupont's jumps... So my bypass does'nt change anything, it acts the same as with master Fader just unplugged and no jumpers.
i'll try tomorrow with other cable, but can you confirm me I did see good on your video
On the Master Fader connector, there are 6 male- pins , counting 1 to 6 from the left to right in your video...
- the center 2 pins are the grounds from both side and has to be put together (pin 3 and 4) ?
- The Lefties and + righties ( 1 with 2, and 5 with 6 ) ?
What else can i Try to really bypass the master fader ? Or is there an issue that makes the volume fall down when I unplug this stupid Master Fader connector :) ?? Thanks again, thanks a lot ...
@@Tetrakan UPDATE Thanks a lot, I've found the good bypass and my Quieter Right Buss problem is definitely caused by the Master Fader ... SO FOR INFORMATION : to bypass Master Fader as in this video you have to shorten the pins "crossing them" like the master fader cables are !! From Left to Right (as visible in the video )
PIN 1 with PIN 5 (left buss) PIN2 with PIN 6 (Right Buss) ... PIN 3 with PIN 4 ( Grounds) .. So glad because my stereo issu looks to be a Master Fade issue only !!! I'll try to clean it very soon .. So cool !
Hi Tetrakan, thanks for these fantastic videos! I have a couple of 244s which both have very noisy audio if using headphones via the Phones out on the unit, but sound clean if I use the monitor outs to a mixer and then use the same headphones out of the mixer. The noise I hear directly out of the 244 Phones is a constant wall of hiss or white noise which is present immediately after power up and not affected by what is happening in the unit (playback, recording etc)
This makes me think there is an issue in the headphone circuit. I've also read a few other accounts online where people mention say Tascam used noisy headphone amp chips in this era.
I have inspected the headphone chip and there is no obvious visual problems like in this video. I've also cleaned all pots which reduced random pops and clicks when turning the pots but has not affected the consistent hiss.
Would you say in your experience that this loud hiss is the expected behaviour/quality of the Phones out audio?
Hi, to follow this up I have found that on the Playback board that the socket for the headphone connection (P801 on the board) shows continuity between the Left, Right and Ground solders. I'm not super experienced with this stuff but I assumed that each should be independent/discrete of one another? It feels like continuity here would be a reason for the ground to be creating issues in the audible L and R channels being output to the headphone jacks...
Hey, sorry for the slow reply. Id expect those three pins to be discreet from each other, yes. You will find some headers connectors or IC footprints where there is continuity between more than one pin, but only because there are multiple connections to circuit ground: for example on a 4 track the connectors for heads usually have 4 connections to ground, one for each tape track. But on the headphone socket I'd only expect a sub 50 ohm resistance to the chassis from the ground pin, with resistance between the left and right pins and chassis or other circuit ground locations being either infinite or at least in the mega ohm range. If you're not getting that, follow out the schematic and look for components from the left and right audio paths to ground, make a list, and test those components for shorts. It's usually a capacitor, semiconductors less often, and rately durable components like resistors, but there's always some black Swan I've never seen before so keep an open mind!
@@Tetrakan after reading the manual a bit more closely about 244's BUSS MONITOR and TAPE CUE being somewhat independent, and then doing some more testing (just playing instruments and monitoring them via phones) I think the phones output is actually fine on the 244.
I'm used to a 424 which from memory the Monitor Level acts as a master volume out to the phones, so on the 244 I expected the Buss Monitor to do the same. Which meant I was probably setting combinations of Buss Monitor and Tape Cue that would either doubling a recorded signal on playback, or introducing more noise from turned up Tape Cue when there was no recorded material to monitor.
Hope that makes sense! Thanks again for the response
@@somepostman glad you got to the bottom of it, happy recording!