How to fix Blackstar Amplifier Hum HT5 and HT5R
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- čas přidán 8. 09. 2024
- Follow me through as I do a 'live diagnosis and fix' on this Blackstar HT5R which had a horrible mains frequency hum and highly distorted output. It took me a while but I got there eventually!
I made a video saying pretty much exactly what you've said here, rightly, and got a swarm of Blackstar fanboys and bots saying I didn't know what I was talking about. Building equipment destined for landfill when a single component breaks is not a state of affairs guitarists should be willing to accept, particularly when previous generations of amplifiers are still around from as far back as the 1930s. I hate this throwaway stuff.
It's helpful when sucking solder off a component leg to first reflow each joint with fresh flux cored solder then deploy the solder sucker (self heated type or plunger). This refreshes old crystallised or oxidised solder and helps the joint to clean up more completely so the component is ready to fall out first try (unless hot glued down :) Hope you find this is effective. I like your relaxed and composed enthusiasm, it really makes for enjoyable watching. When you have an employer wanting/needing ever faster diagnosis and repairs the fun can get somewhat diluted. :)
The holes drilled in the PCB between the legs of the FETs are a Blackstar-approved mod to deal with the fact that the heat generated by the FETs causes the lacquer on some earlier PCBs to go conductive over time, which gives rise to some peculiar problems. I've seen it done more neatly than that though.
Marshallitis
Bloody nightmare when somebody has been in there bodging!! Great work Young Stuart! 5*****!!
Thank you for saving another HT5R from the scrapheap, couldn't have done it without your diagnosis. As well as a neighbour (also) called Stuart with an oscilloscope and electronics expertise!! the dead smoothing cap in my amp was actually 400v and 100uF, so replacing with one with same value. NB if ordering a replacement cap, the cap height of 32mm is the max or the board wont fit back in..
Why do folks always say SMD gear is unfixable? I learned how to do it from a couple youtube videos and a modest investment in tools (tweezers, fine soldering tip). I have hand built a few synth modules now and made repairs and mods to other SMD gear. I'm just a hobbyist not a pro tech, but I find it actually easier and faster than through hole now.
Great video and repair, just goes to show how useful an oscilloscope can be.
I will definitely be watching more of your videos 👍
Another amazing fix. Love watching those videos
Stuart,
Thanks again for fixing my amp. Really going far beyond my expectations.
I bought the amp new and it has never been repaired so the FETs must have been soldered in like that.
Seeing some of the soldering I am surprised it has lasted this long. Trying to remember how old it is - at least 7 years old.
Paul
PS glad I give the casing a good clean!!
Also I did notice the problems with the knobs - I do not use the overdrive so do not use the knobs on this section alot.
Hi Paul, they overheat, that's the problem. Then the solder joints give way. No more boards available for these amps now, so hello landfill...
Diagnostics is a science, thank you Stuart for sharing your process even though we might take on the basics of testing first I'm sure most companies building amps would possibly prefer complete amp replacement due to the amount of opp amps mini transistors etc on the PCB boards these days. Shame but it's also cutting out people repairing amps as a Tech myself. Sooner than later the new generation of amp production will have non replacement parts and pcb tracing a distant memory to hide the magic...Hopefully you might explain the use of an osciloscope how and what it is indicating. Reading voltage and showing how continuity may throw out testing results without a Olly scope. There so much cheaper today than 40 years ago..
Thank you for that very enlightening repair Stuart. I was mildly surprised that the output FET's did not have their own small heat sink !.. Considering 'heat' is an identified enemy that needs countermeasures to deal with , I'll award the designer of this amp 1 out of 10 for this oversight, but 10 out of 10 for your repair.
Excellent video. You diagnose and explain it all so well.
Many thanks
A technique i use to remove stubborn knobs is very similar to yours. Instead of a screwdriver try needle nose pliers, use one jaw on each side of the shaft and as the jaw gets thicker it works like a wedge and slides the knob off the shaft using even pressure on back of the knob . Works for me, you may want to give it a try
I'll give that a go thanks. Sometimes a squirt of WD40 does the trick also
@@stuartukguitarampguy5830 thanks for all you do Stuart. I really enjoy your videos and learn a lot. Cheers.
Very well done - good analysis and good work
Interesting video, ta for posting.
Was interested in a Blackstar amp, but put off now.
Great whilst they work. A bugger when they don't!
I just watched your video again and used the part number you provided. Cheers
Have an acoustic guitar with a preamp for the piezo.
It started making a loud hiss. I did a similar thing, but used one wire. Started touching the two leads on each capacitor and found the one that made the hiss go away. I just solder a wire from one lead to the other and called it a day.
Nice one!
I needed a board for a dsl40c , contacted Marshall n they said they dont have those any longer , so its lookin like its gona be a thing . As they say , they dont make em like they used to . Thx Stewart .
The Blackstar HT series of guitar pedals use a similar SMPS to power the valve and have the same problems with blown switching mosfets. When they go, they really go, burning through the pcb. I ended up doing a new mini pcb to replace the HT power section in an HT Delay pedal. There must be an inherent weakness in the design.
Yes I totally despair when I see such basic design errors as this.
Hi Stuart, is it my imagination, or do those two electrolytic capacitors adjacent to those two power Mosfets look like their tops are bulging a bit?, I might be mistaken though.
Oh how I wish you could look at my Blackstar ht Stage 60 212 mkii. Just over a year old and it went completely side ways on me...a really bad fuzz type sound with a strange subharmonic over tone with a vibrato/Tremolo effect. To say I'm bummed, is a huge understatement.
Subscribed. Great channel Stuart. I love your methodical approach. However, looking at the dubious if not downright awful quality control of this amp I had better not tell my son-in-law who has I think a couple of them 😬. Or is this just not par for the course nowadays??
I find the easy way to remove those surface mount resistors is to get a good blob of solder across the resistor and it will get stuck to your soldering iron. Give it a try if you have a donor board. Then just clean the pads with braid and solder the new resistor in place. A bit of solder flux helps alot not getting solder bridges on nearby components.
Ok good tip thanks Daniel.
Excellent video!
Although those blues striped Caps from Jamicon are defenately NOT crap, those next to the FETs look blown as well....
Great work!
Would you happen to have the schematics for the MK2 version of this amp? Need to know the FET part numbers. THANK YOU for the excellent video!
I've got a Blackstar Studio 10 KT88 here with an output more like 1w than 10, the valves seem OK as I have substituted them to no avail, do you know the correct bias voltage for these amps? Bias seems to be derived from a FET (although this measures OK on a cheap Chinese tester; could the IRF830A be a problem?). Blackstar won't give out a schematic for this which makes it difficult to diagnose.
Thoughts on the HT-5R MkII amps? Have you seen their components? The say there are improvements.
First
You need to be careful when measuring with the help of the oscilloscope
tektronix 2445
With the help of X1
You could burn the
The front end of the tek 2445 with 150 v
on high volt use only X10 .
Second thing
When using the de solder gun add new solder to the pcb joint
With a new tin for the gun it will be much easier to pump out the tin .
This is basic things in soldering
I specialize in IPC610A military grade soldering
In any case good work on the diagnosis and repair
Everything I said was not meant to offend
Just friendly advice
You'd advise adding new solder to each and every joint to be de soldered? Even if using a basic soldering pump? That's a genuine question, I'm interested in your answer. Thanks
@@chrisdee5032
When you add new tin
This allows you to remove the old tin much easier
Usually in PCB boards
It is lead free and is more difficult to remove
and requires a higher temperature
@@chrisdee5032 Yes. But by new solder, High lead content solder, 60/40. The silver solder used today takes much more heat and hardens faster, and it becomes brittle over time and harder to remove. Adding Lead/tin creates a much softer mix and gives you just better work altogether. Less heat on components being a huge plus. and then finish off your job with some alcohol. Some for cleaning and some just to reward yourself or calm your nerves, whichever applies.
Hi there, my ht5r is needing some new MOSFETs. Will irf830 replace smk830 without any problems? If so would you mind telling me where to buy the exact type that you use yourself. I've got a bit confused with the various types listed in certain sites. Any advice would be much appreciated. Regards Simon
Very informative . Thank you .
My ht5 has stopped working with the headphones plugged in, the sound still comes out of the speakers and only one side of the phones, but no silent play, is it fixable or scrap? Cheers
Korg sells the boards now
So
I just bought a used HT5R from a guy and now wondering
Are these amps all for sure doomed to hell or can anyone attest that they are good reliable amps?
Awesome. Is the HT Metal the same ???
So did this job cost more than the amp is worth?
Isn't that capacitor near the fet not bulging?
Looked like it to me, too.
Hello
Stuart
ask for advice repair.
I have a problem heat mosfet irf840 .
temperature 57c. hot untill c 39 22uf 450v
resistor r10 10k 3w
i m not touch.
I dill between pin mosfet and change new mosfet irf840 tr2 tr3 risistor 22k r38 r39 and capacitor 4.7uf c45 c46
not finish repair hot
masfet and capacitor
I m afraid blast capacitor and shock
mosfet.
sound it good but very hot mosfet and capacitor v. pin drain tr2 tr3 190v tp 6 tp7
-23.5v grid 46mv at D20
I change c39 up voltage from 190v up is 260v at drain tr2 and tr3 finished work
I m test 1hour no problem capacitor change 85`c up 105`c
resister r38 r39 temp 40`c temp tr2 tr3 48'c install add heat sink Thank you.
unfortunately most new amps have cheap and nasty caps in. IC caps are a prime example in the Fenders and Peavey. Probably the worst caps ever!! The manufacturers make the money and the poor end user get the shi**y product and all for the sake of a few pence!! All of my amps have F&T and Dubilier caps in. I have never seen one of either fail
dude use new caps always
What a mess wow
A jewelers loupe is the name of the eye glass thingy ma bob