I do have a soldering iron and have done a bit of low-level electronics things(guitar pickup installation), so if it's definitely that, I could probably manage it.
The problem really is being able to determine that that is the issue.
Yeeeah, time for a pro I think!
The problem really is being able to determine that that is the issue.
Yeeeah, time for a pro I think!
Easier get idea with scope waveform.
Amp looks clean and gone through.
So likely end of life semiconductor or related circuit.
Current source ,input stage etc etc.
Its only guesses without data.
very unlikely a cap issue. looks gone through.
Amp looks clean and gone through.
So likely end of life semiconductor or related circuit.
Current source ,input stage etc etc.
Its only guesses without data.
very unlikely a cap issue. looks gone through.
Ok, interesting.
The fact that the seller mentioned that he'd recently replaced the caps also backs up your point about them looking fine.
Totally understand that you need the data to really figure out what the issue could be. Sadly, I wouldn't really know how to collect that data! (useless, I know)
The fact that the seller mentioned that he'd recently replaced the caps also backs up your point about them looking fine.
Totally understand that you need the data to really figure out what the issue could be. Sadly, I wouldn't really know how to collect that data! (useless, I know)
You could have a word with this guy: https://www.amplabs.co.uk/. I found him most useful when checking the history of one of his modded 303s.
The 306 PCB uses unplated holes, so dry joints are very likely.
The later amplifiers use very similar layouts and largely (all?) single sided, but with plated through holes and a silkscreen
The later amplifiers use very similar layouts and largely (all?) single sided, but with plated through holes and a silkscreen
I find it unsurprising that old Quad gear like the 33 and 303 used single sided boards. But when it got to the 405, 34, 44 and later dumpers like the 606 there was no excuse to not use double sided boards. Single sided boards festooned with wire links was very strange at that time.
But Cambridge Audio into the 90s used single sided boards. At one stage there was a reliability issue relating to the smoothing caps capable of wobbling and breaking the contact with the pad, or tearing the pad from the track. The solution was the stick the capacitors to the board with hot melt to stop them wobbling.
But Cambridge Audio into the 90s used single sided boards. At one stage there was a reliability issue relating to the smoothing caps capable of wobbling and breaking the contact with the pad, or tearing the pad from the track. The solution was the stick the capacitors to the board with hot melt to stop them wobbling.
I suspect they didn't want the risk of changing technology - there are risks associated with the change disrupting the production, which is never attractive to a manufacturer, and double-sided is more expensive, its not like audio needs double sided is it? Suspect it was just reduce risk, reduce cost.
Depends.
But agree , depending on the design single sided almost seems better.
Some of the better engineers probably still use to hand drawing traces.
Roland Boss did some extremely complicated circuits and many kept
to single sided. Works of art really
Biggest improvement is fully plated hole through sleeve.
far as vibration / shock damage and reliability. Musical Instrument amplifiers
have a lot to teach to some approaches
But agree , depending on the design single sided almost seems better.
Some of the better engineers probably still use to hand drawing traces.
Roland Boss did some extremely complicated circuits and many kept
to single sided. Works of art really
Biggest improvement is fully plated hole through sleeve.
far as vibration / shock damage and reliability. Musical Instrument amplifiers
have a lot to teach to some approaches
Both Quad and Cambridge Audio at that stage were cottage industry companies. I visited Quad in the early or mid 80's when a good friend went to work there. I spent quite a bit of time talking to Mike Albinson. He used to hand tape at 4x, and then stick it with a white backing to the end of a dexion shelving unit. Directly opposite that was the downstairs toilet, which Mike had converted into a dark room. Into the door he has screwed a camera lens. On the opposite wall of the toilet he would attach the photoresist coated board. The overall magnification was 1/4, so the board was exposed at the right size. All this was on a sunny day. He'd make an estimate of the exposure time, then develop the board, drill the holes by hand, build and test.
Everything with transistors (33, 303, 405, FM3, FM4, 34, 44, 606 etc) were designed that way.
And that is why Quad boards were single sided until Mike and Peter Walker shuffled off this mortal coil, and Quad moved progressively over to double sided.
In fact the most recent audio thing I designed was four layer. Top and bottom signal traces, buried ground and buried power distribution, Surface mount of course, since most recent high specification op amps are surface mount only.
Any PCB with plated through holes is actually at least double sided. Just that they chose not to put tracks on the component side.
It was about the 606 era that they first went to PTH. The reliability improvement and reduced warranty claims would easily cover the marginal cost. Those jumper links were not free either.
It was about the 606 era that they first went to PTH. The reliability improvement and reduced warranty claims would easily cover the marginal cost. Those jumper links were not free either.
Hi everyone,
So I sent my amp off to Amp Labs - thank you for the recommendation!
I thought there might be some people in here interested in what was going on.
This was part of the report I was given at the end. From what I understand - in my very limited knowledge(!) - it was a driver transistor that needed replacing, amongst some other bits.
It's now working perfectly, in fact, I think it sounds better than it did before!
I'd like to continue the recommendation of AMP LABS, as their engineer, Rob, did a fantastic job and I'd highly suggest you get in touch if you need a vintage amp servicing. ALSO, the prices are very, very reasonable.
Find them at: www.amplabs.co.uk
Action taken:
Full set of smoothing and other electrolytic capacitors tested for ESR and value;
Main smoothing capacitors measure 100% with low ESR and well within
tolerance. Checked bootstrap capacitors for value and tolerance Measure 100%
Checked for dry joints on input sockets and Driver transistors–all ok.
Carried out full signal analysis on both channels to isolate fault/s:. Driver
transistor on right hand amplifier section o/c –replaced. Associated heat-sink
washer replaced. Checked L & R bridge components for THD on both outputs –
result well balanced below 0.07% @ 5W rms/8 ohms on both channels.
So I sent my amp off to Amp Labs - thank you for the recommendation!
I thought there might be some people in here interested in what was going on.
This was part of the report I was given at the end. From what I understand - in my very limited knowledge(!) - it was a driver transistor that needed replacing, amongst some other bits.
It's now working perfectly, in fact, I think it sounds better than it did before!
I'd like to continue the recommendation of AMP LABS, as their engineer, Rob, did a fantastic job and I'd highly suggest you get in touch if you need a vintage amp servicing. ALSO, the prices are very, very reasonable.
Find them at: www.amplabs.co.uk
Action taken:
Full set of smoothing and other electrolytic capacitors tested for ESR and value;
Main smoothing capacitors measure 100% with low ESR and well within
tolerance. Checked bootstrap capacitors for value and tolerance Measure 100%
Checked for dry joints on input sockets and Driver transistors–all ok.
Carried out full signal analysis on both channels to isolate fault/s:. Driver
transistor on right hand amplifier section o/c –replaced. Associated heat-sink
washer replaced. Checked L & R bridge components for THD on both outputs –
result well balanced below 0.07% @ 5W rms/8 ohms on both channels.