Trace Elliot SuperTramp Twin losing power

[Pinchinpete]

Thanks..I had a look but can't find anything....maybe I will replace the components as suggested in #11 just wondered how the values were arrived at?

[oc disorder]

"just wondered how the values were arrived at?"
Good question - maybe looking for the tube had a detrimental effect !
You can't believe everything you read on the net !
Hope we are looking at the same schematic - Super Tramp & Twin.pdf
Supertramp 80 watt output stage.
For starters I assumed (incorrectly) they were TO3 mosfet outputs.
Renesas look like they still sell them
http://documentation.renesas.com/eng..._2sk1056ds.pdf
http://documentation.renesas.com/eng...7_2sj160ds.pdf

The equivalents are

P-channel MOSFET,BUZ906P 8A 200V
RS Stock No. 841-132

N-channel MOSFET,BUZ901P 8A 200V
RS Stock No. 841-075

same as used in the UK Ashdown bass magnifier

or these 2SK1058 = plastic ECX10N16
2SJ162 = plastic ECX10P16

which are no longer available so ECX10N20 and ECX10P20
ECX10N20
ECX10P20

The part numbers were already there 1058 and 162.
Just the suffixes were missing.

The BF422 and 433 were written below the diagram.

If the amp was working it is doubtful the mosfets were faulty as J M Fahey
mentioned.
I was initially attempting to indicate the cost of the parts .
Check the diodes as a starting point there's only 4 then the BF 4**'s.
R16,R17 and C4 and C8 worth checking intially too.
I'm guessing the zeners are BZX55C12v
and the diodes are 1N4148 as used in other designs of theirs.
If the heat sink paste is messy ,(it should be soft and easy to remove as compared to the glue used to hold down larger components)maybe you could tidy it up and check there is no connection between the middle pin (source)
and the heatsink. It should be insulated with a mica washer.

J M Fahey's suggestion of a replacement drop in module is very sound advice.

[Pinchinpete]

I am not sure this is a correct schematic as the amp has a valve on the preamp section which I have replaced (12AX7) and its a twin...I have searched for it but cant find it on the net although this is quite a common amp from the 90s...however I will be getting it back from the repair guy tomorrow so I will take it apart and look at the component values...then come back for more help.

[J M Fahey]

Hi pinchinpete.
Even if you don't have the *exact* schematic, remember amp manufacturer's are like Mc Donald's: out of the same old tired 5 or 6 basic ingredients, every other month they make "new, improved, fantastic!! burgers"
I'm sure your amp is the Tube Tramp preamp (without chorus) + the Twin output stage, close enough for service.
Besides that, all (well, 99%) of those 2SK/2SJ power amps just used the suggested Hitachi schematic so they are all the same.
In that particular case all they modded was to add the 0r33 resistor (or a similar low value one) from speaker minus to ground, to "valvestate" it, no big deal.
So I think you *can* repair it, depending on your bench skills.
If you don't want to waste time, the British Award Session company made a very popular (Sessionette 75) very good sounding amp in the 80's, which used a Mosfet power module, unavailable today.
To back their faithful customers, they offer an inexpensive drop-in module, which is just bolted to the chassis or heatsinks and needs only 5 wires: +V, -V, Ground, In, Speaker+ or "hot" ; I would add a Speaker - direct to ground at the power supply .
*or* you can try to repair the original one.
Post some pictures of the power amp area and heat sink, to see what space is available there.
EDIT: forgot links:
http://www.award-session.com/pdfs/SG...structions.pdf
http://www.award-session.com/pdfs/SG75_Power_module.pdf
http://www.award-session.com/

[Pinchinpete]

I have my amp back and the power transistors are TIP 35c & TIP 36C which are pretty easy to get hold of...I have also found that a large green resistor has burnt and its coming from the 4th pin of the valve as you look at the valve from the base or pin end..the valve is a 12AX7EH...so my logic is that the resistor may have been causing the original problem and the power transistors caused after wards by the so called tech who looked at the amp.

I have decided to replace these components then take it from there...just one small problem the green resister doesn't show a value other than its 5% tolerance as the other is obscured by the burning and I wondered without the aid of the actual schematic is there an educated guess from anyone as to what this might be.

[J M Fahey]

Big and to pin 4?
Logic says it's a voltage dropping resistor that lowers amp's +B (around 40V) into 12.6V needed by the valve's filament.
Follow traces : one end must go to the positive main supply, the other to pin 4 in the socket. Pin5 should go straight to ground.
There are other options but that's the most efficient.
Are you sure the resistor is bad?
They work hotter than H*ll and often toast, themselves and the board, yet keep running.
Does the tube light? Does it have 12V across pins 4-5? What voltage do they show to ground?
If so , leave it alone.
If don't, measure and post +B to calculate R value.
Confirm that tube pin 5 goes to ground.
Of course, Logic does not *always* rule.

[Pinchinpete]

Just reading back my post I can see 1 was a little vague...looking at the valve holder in the circuit board with the valve out it is the 4th pin on the right going anti clockwise.....I can't see direct trace back to +B,however looking at the resister the solder has run down its legs to the body and it quite messy....I have removed it and measured ..it shows 120ohm but when wiggling the wires the meter drops to zero so may be faulty..

Just going back to my original fault which was a sh*tty sound at reduced volume could this be related?

[J M Fahey]

Maybe.
Replace it carefully, take care of the PCB pads, plug the tube, turn amp on, and measure voltage on pins 4 and 5.
Measure Pin 9 too, as a backup check.
From below board (pin side) count clockwise; from above (tubeside) count counter-cloclwise.

[Pinchinpete]

I feel such a fool...I disconnected the leads from the circuit board so I could access this for the repair and have replace the 2 power transistors and the burnt out resister but I have mislaid the piece of paper I wrote down what leads went where....Most I am ok with but I have the power transformer with 4 leads two red & two orange (plus the earth which I understand)...however the connectors on the circuit board show 2 as AC and 2 as HT ...I think the reds go to HT but just wanted to double check ......is there a way for me to quickly work this out?

[J M Fahey]

Grab your handy multimeter.
Scale 200VAC , black to ground (the color with only one wire) red to , sequentially, each of the oranges, each of the reds.
If any "overranges" switch to 500VAC scale.
Post results so if you lose the second paper, you can always check here
Of course, try to avoid forgetting username and password

[Pinchinpete]

Deleted post in error

[J M Fahey]

Hi pinchinpete, don't worry, I hadn't closed my window, it said:

Interesting....no power to the transformer so tracing back it appears that the kettle plug socket has suddenly developed a fault as the power is OK to the plug end of the lead but nothing from the socket tabs.....I don't understand how this would suddenly stop working as I can see a fuse or any links.....would this "blow" as part of a system overload?

To think when I took this in to the repair shop is all that was wrong was sh*tty sound!!!!

Yes, you are right.
I'm sure the male mains connector has an internal fuse, probably in a little "drawer" under the actual metallic pins.
You can't pry it open with your nails, you need a small screwdriver.
It's there somewhat hidden for safety reasons, it's also blocked while the power cable is still there.

[Pinchinpete]

Replaced the fuse and it blew straight away ...this is now beyond my capabilities so I will bin it and use this an an opportunity to purchase something better.

Thanks for all the help

P-Pete

[Grimsleaper]

I know this is an old thread and I am a new member but I am bumping it because I have the same amp and I have a similar problem, I will play for a while then whammo, cuts out. So I pulled the amp from the cab and played it last night, when it cut out I plugged in an instrument cable to the return jack on the effects loop, just the cord, no effect. Back in business. I unplugged it the return jack and it went out again. This time I watched as I plugged the cable into the jack, as the tip made its way into the jack and touched the rear contacts of the jack it closed a circuit and the sound came back on again, without that circuit closed the sound was very much gone.

I can see on the schematic that there is an extra contact on the return jack, but I don't understand what the function is. I read in the manual that there is a bypass when you plug something in to the return but all of the amplifier's controls work just as they did before.

I hope Pete hasn't scrapped his amp if his is the same issue.

Thanks for reading.

[SmogFighter]

Grims....

you should be able to clean and adjust that rear "leaf switch"s contact. that should get your sound back.
R