Bit of a mystery this one but lots of good learning points as I struggle to unravel it!
Пікірлер: 55
@michaelevans3852 Жыл бұрын
Happy to see you post again Stuart. These amps do look quite complicated. I have begun to use number tape when removing many wires at a time. I also take many pictures and draw a diagram as I have seen you do. I'm getting better at this and am enjoying it as a hobby. Thanks again for sharing your expertise. Mike
@stuartukguitarampguy5830 Жыл бұрын
Thanks Mike I have writtten strip down procedures for these amps as there are a huge number of inter-board connectors.
@bobparker4989 Жыл бұрын
Glad to see you back Stuart.. I've had one for these amps to work on I must agree to many plugs to cause problems.another great video
@stuartukguitarampguy5830 Жыл бұрын
Thanks Bob.
@DrWatts-bi1jv Жыл бұрын
I wondered where you'd gone, Stuart 😊 Good to see you back. Always check the 16 Ohm socket, it switches the other two sockets off if something is plugged into with if them to avoid someone plugging another cab in, causing an impedance mismatch and seeing the output transformer off. If the amp had been used at 8 or 4 Ohms for a few years, the 16 Ohm socket will burn up and present an open circuit, causing a flashover, blown cathode resistor, burned valve socket or worse... ALWAYS CHANGE THEM with every service !!! The other common problem is poor valve selection. The DSL & TSL's have very high HT and a lot of valves can't deal with it. I've seen several that have come in fitted with JJ's and the Bias is running away, not because the board is faulty, but because the valves are crap and can't handle the voltage. Shove a decent set of valves in there and the amp will settle down beautifully. Personally I'd have changed the output valves, but I guess it's 'horses for causes'. It certainly looks like it's had something spilled through the top. I don't think I've ever seen a chassis looking quite so distressed 😂 FYI: The factory Bias setting is 90mV per side using the connector on the rear of the chassis, but personally, I usually set them for 80mV. 45mA per valve, what were they thinking 🤔 Mind you, with such high HT I guess everything else goes up with it... Valves are a lot like incandescent light bulbs, they can last fifty odd years or they can blow up straight out of the box and they can certainly have intermittent shorts. I've got an old saying 'Just because it's new, don't mean it's any good' - and that certainly goes for valves 😂 Anyway, I look forward to the next 'terribly designed' amp you work on and all the best, Stuart. Squidgy squeeze
@stuartukguitarampguy5830 Жыл бұрын
Hi thanks for the response. I didn;t know that about the 16ohm socket, that's a really good tip. Yes I did know about the valves after suffering a lot of blown JJ EL34s. The JJs just can't take the plate voltage. I use Marshall EL34s which I think are EL34B. Also jj EL34II are ok. Thanks again for your very useful and knowledgeable contribution.
@DrWatts-bi1jv Жыл бұрын
@@stuartukguitarampguy5830 The sockets are a quid each and it's just not worth wasting the time. In the bin with the old one and in with a new one. I see it all the time, in fact I'm doing one right now 😂 Take care Stu
@stuartukguitarampguy5830 Жыл бұрын
@@DrWatts-bi1jv Awesome thanks for the tip.
@BradsGuitarGarage Жыл бұрын
I advise jumpering the ground shunt contacts on the 16 Ohm jack. There's no reason to break that connection when plugged into the 16 Ohm jack and I consider it a PCB layout error.
@stuartukguitarampguy5830 Жыл бұрын
@@BradsGuitarGarage Thanks Brad I've never come across this 16ohm jack issue before so it's a useful tip
@jerryogle8798 Жыл бұрын
Great job Stuart glad to see your doing well.
@stuartukguitarampguy5830 Жыл бұрын
Thanks!
@pda49184 Жыл бұрын
That was tricky Stuart !! .. It always worries me when I see a 'blown' component and there's no hard & fast clue as to what caused it to blow. (apart from valves of course who operate by their own set of rules 😅.... Great video and nice to see you back on again ..
@stuartukguitarampguy5830 Жыл бұрын
Thanks Pete yes I also like to find out exactly what went wrong. I don't like mysteries. I think I did this one a few months ago now and it hasn;t come back!
@alexdeleon7135 Жыл бұрын
I'm glad to see this latest post, Stuart. You were absent long enough to cause concern. This was quite an enigmatic amp to be sure. I too detest the DSL, and TSL series because of the ever-present reliability flaws. Coincidently, I am curious about how parts availability will be effected by the Swedish purchase of Marshall. Have you experienced any change in the parts matrix? Enjoy what's left of the weekend, and remain in abundant health. Cheers!
@stuartukguitarampguy5830 Жыл бұрын
Thanks Alx, yes I went on holiday then had a huge backlog of amps. I hadn't heard that Marshall had been purchased by the Swedes? How odd!
@edwardhannigan6324 Жыл бұрын
Excellent video Stuart..Lots of info and procedures towards the remedy..Thanks for sharing once again..Keep well..Ed..uk..😀
@stuartukguitarampguy5830 Жыл бұрын
Cheers Ed.
@vintageguitaramp_guitarteacher Жыл бұрын
Hello Stuart, good to see you back. Did you ever get to the bottom of what had been spilt inside? Maybe some conductivity on the valve pins on the end valve but when you removed it, it cleared the fault? Mending those things is never fun. Another great video. Good to see you back online. Take care.
@stuartukguitarampguy5830 Жыл бұрын
Hi Thanks for the wishes. No I never got to the bottom of it. The customer denied all knowledge!
@kurtsnider83658 ай бұрын
TY Stuart After seeing the Stacked PCB's one would question reliability and longevity...
@stuartukguitarampguy58308 ай бұрын
Yes, amazingly though they do see to limp along!
@donnyboy9114 ай бұрын
nice vid.... ran across similar issues...
@zbaby82 Жыл бұрын
Good job. It looks like it was just a faulty resistor. I have two Marshall TSL60s. I think the DSL and TSL series sound good when they're working. Personally I think they made them too complicated. Too many channels, too many knobs, too many features and too many switches. I believe they were competing with Mesa when these were designed. I play my TSL60s through the lead channel 99% of the time.
@stuartukguitarampguy5830 Жыл бұрын
YEs I really don;t like the TSL and DSL, there are over 150 interboard connection points, any one of which can cause an issue. No idea what they were thinking designing it like that.
@pickholder6189 Жыл бұрын
For a couple of sections of this video you had no speakers plugged in or a dummy load? One issue I have with DSL/TSLs is the solder underneath the mains fuse and HT fuse holders. It is worth taking out the small board with the IEC mains connector on and checking the solder. TSL amps are trash, terrible.
@stuartukguitarampguy5830 Жыл бұрын
Hi Ok thanks for the tip on the small board. Did you see the earlier post about the 16ohm socket? That was useful too. I only plug in a speaker or dummy load if I am going to put a signal through the amp. It's not needed otherwise.
@stephengray9207 Жыл бұрын
Well Done. Personally, I could not sleep till Id removed all the boards, but the cost would have been completely unreasonable for the customer. Viewers and customers don't understand the commercial reality of such repairs. I suspect that the spill ran through to the bottom of the new board you installed and caused an short. But the time it takes to do that is well beyond the fee the customer would pay for. Chances are that the liquid has dried out and wont cause the issue again anyway. But it could be corrosive and worsen. who knows! Its always a trade-off when we repair a product that is price sensitive for repair as to how far we go to be sure we got it nailed. I bet you didnt charge for all the time you invested. Anyway, this is the commercial reality!
@stuartukguitarampguy5830 Жыл бұрын
I seem to recall I did check the board and it wasn't contaminated. So far it's stayed out there!
@tomfoolery20829 ай бұрын
Would u know where a person might purchase a replacement board for a dsl 40 C . If i knew then i would not have bought it . Appreciate ur channel . Iv learned alot . Thks
@stuartukguitarampguy58309 ай бұрын
The only possiblility is Marshall but I doubt they have one. Worth asking them though.
@SumYungai-AXE Жыл бұрын
I thought the DSL and TSL were notorious for the bias drift problem which generally requires a bypass and a new bias PCB replace. A bias drift would have exhibited as a runaway plate current and burnt cathode resistor makes sense. There are after market boards and instructions for it.
@stuartukguitarampguy5830 Жыл бұрын
Hi Yes that's a common problem but only in earlier issue boards. I think this one had a late issue, either that or I had changed the board on a previous visit, I can;t recall.
@gingercat777 Жыл бұрын
Needs more knobs 😅😅
@stuartukguitarampguy5830 Жыл бұрын
Hmmm.. good idea! I reckon I could squeeze a few more in there. How about 'Sparkle' for all channels?
@bluesplayer59 Жыл бұрын
I had one for a short while and sold it because it didn't sound that good . Not one of Marshalls better amps 😢
@stuartukguitarampguy5830 Жыл бұрын
Yes too complicated in my view.
@tjsogmc Жыл бұрын
I never like it when I can't find the root cause of a component failure, Perhaps it was a faulty resistor? It's possible that of the 30 million they make every year, that was a bad one from the factory and it just gave up after a few hours of use. As they say "time will tell". ;)
@stuartukguitarampguy5830 Жыл бұрын
Yes agreed, I hate not knowing why an amp failed. The other one I get all the time is "The amp failed on a gig, no sound at all." Comes in to me, endless soak testing, banging, waggling...nada, amp is totally solid.
@charlesjoynes9497 Жыл бұрын
Are very inspiring! Thank you!
@stuartukguitarampguy5830 Жыл бұрын
Thanks Charles.
@SuperSeanXXX6 ай бұрын
All new sensor 12ax7s.....tung sol, electro Harmonix, sovtek lps, mullard reissue....they are all microphonic new
@stuartukguitarampguy58306 ай бұрын
That's interesting news - and not good!
@waynegram8907 Жыл бұрын
STUART, How can you measuring the transconductance GM of the power tubes to match them?
@stuartukguitarampguy5830 Жыл бұрын
Hi. A longish answer to this. Firstly, when I revalve for a customer I just buy in a matched pair/quad or whatever so that solves the problem. I don't have the in house equipment to test transconductance (basically gain) of power valves but I also don't believe it's that important. Here's why. The gain of a power valve is actually quite low (compared with a preamp valve) and so any small difference in gain doesn't have THAT much effect on the overall signal. And in any case, the effect it DOES have would result in a very small amount of distortion on the signal. What??? Distortion in a valve guitar amp?? We wouldn't want that now would we! The only time it might matter would be in a HiFi amp but even then, cynic that I am, I wonder why the **** anyone would want a valve amp for HiFi? Back in the day we were chasing 0.001% total harmonic distortion for our HiFi amps. A valve HiFi amp would have something like 1% distortion! So why do HiFi buffs go for valve amps? I believe the answer is they like the distortion. They perceive it as 'warm'. So it's exactly the same reason as guitarists prefer valve amps - they don't like the clinical, clean sound of a transistor amp, they like the distorted 'warm' sound. just my view of course!
@waynegram8907 Жыл бұрын
@@stuartukguitarampguy5830 If you measure AC voltage on the grids of the power tubes and measure the AC voltage on the plates of the power tubes this is Vout/Vin= GAIN but you have to convert it to Gm transconductance how so?
@stuartukguitarampguy5830 Жыл бұрын
@@waynegram8907 Hi Wayne Could I ask why you particularly want a transconductance figure rather than a gain figure?
@waynegram8907 Жыл бұрын
@@stuartukguitarampguy5830 The power tubes data sheets say transconductance figure which should GAIN MATCH the in-circuit Gain
@divebomb99 Жыл бұрын
I've found that pouring Diet Coke straight into the vent causes far less failures than regular Coke. Surely this was a case of Diet Coke. 🙂
@stuartukguitarampguy5830 Жыл бұрын
Thanks for that, I'll remember that tip.
@motokev2727 Жыл бұрын
Looks like acid
@motokev2727 Жыл бұрын
After watching most of your videos, I will only buy a handwired amp. Stay away from these complex gadgets.
@stuartukguitarampguy5830 Жыл бұрын
Good plan!
@sting11117 ай бұрын
sovtek. lps or long plate work good in v3. they can be noisy in v1 and v2. i just learned this is a possibility.