Ashton Amp Repair Advice.

[Sonic Mountain]

Here's some more pics. Just tried to get the whole board in sections. Let me know if you want to see something specific up closer.

Yeah I'll go over and make sure they are discharged before I do anything. This is exactly why I posted, I probabyl wouldn't have thought of that. I assume the two large black caps at the end of the board there would be prime suspects for discharging?



Yeah, built in transformer.

The fuses appear to be intact, but I will confirm that after work with the multimeter.



It'd be great if it just needed a switch replacement. That's the kind of achievable repair I was hoping for. I guess I just look for continuity when it's in the 'on' position?

[dave.king1]

Here's some more pics. Just tried to get the whole board in sections. Let me know if you want to see something specific up closer.

Yeah I'll go over and make sure they are discharged before I do anything. This is exactly why I posted, I probabyl wouldn't have thought of that. I assume the two large black caps at the end of the board there would be prime suspects for discharging?

The filter caps are the ones that hold the big charges and at far higher voltages in a valve amp

Ten Commandments of Electrical Safety
(1) Beware of the lightning that lurks in an undischarged capacitor lest it cause thee to be bounced upon thy backside in a most ungainly manner.

(2) Cause thou the switch that supplies large quantities of juice to be opened and thusly tagged, so thy days may be long on this earthly vale of tears.

(3) Prove to thyself that all circuits that radiateth and upon which thou worketh are grounded lest they lift thee to high-frequency potential and cause thee to radiate also.

(4) Take care thou useth the proper method when thou taketh the measure of high-voltage circuits so that thou doth not incinerate both thee and the meter, for verily though thou hast no account number and can be easily replaced, the meter doth have one and as a consequence bringeth much woe upon the supply department.

(5)Tarry thee not amongst those who engage in intentional shocks for they are surely non-believers and are not long for this world.

(6) Take care thou tampereth not with interlocks and safety devices, for this incureth the wrath of thy seniors and bringeth the fury of the safety officer down upon thy head and shoulders.

(7) Work thee not on energized equipment, for if thou doeth, thy mates will surely be buying lunch without thee and thy space at the table will be filled by another.

(8) Verily, verily I say unto thee, never service high-voltage equipment alone, for electric cooking is a slothful process, and thou might sizzle in thy own fat for hours on end before thy Maker sees fit to end thy misery and drag thee into His fold.

(9) Trifle thee not with radioactive tubes and substances lest thou commence to glow in the dark like a lightning bug.

(10) Commit thee to memory the works of the prophets, which are written in the instruction books, which giveth the straight info and which consoleth thee, and thou cannot make mistakes.

[BigDaddy]

Good pics. The heat shrinked covered bit in your 2nd pic may also be an in-line fuse. It appears to sit between the IEC power socket and the switch. Have a close look in there too. Those 2 big caps are the filter caps. The leads are underneath so u would have to lift the board to access them.

Regarding the switch, you can check that with your meter.

[Sonic Mountain]

Hey BD.. do you mean this black block circled in red?




That's a rubber cover that goes on the back of the switch.

Will discharge the caps and should get a chance to confirm the switch and fuses in a little while

[BigDaddy]

Be careful of the x2 transistors when you are lifting the board (see pic) - these are those black square looking things screwed to the aluminium heat sink. Q3 designates one of them in your pic. They will likely have white heat sink compound behind them to help couple them to the aluminium plate. Don't wipe that off.

No worries re that cover. I thought it may have been an inline fuse. Let's hope it is the switch.

[dave.king1]

Silver heatsink paste is available at Jaycar for a pittance if you need it.

[Sonic Mountain]

I actually have a tube already from doing points to electronic ignition conversions on my various Vals.

OK so a bit of progress. The fuses and switch all appear fine according to the multimeter, the fuses have continuity and the switch only does when its in the 'on' position.

Will have to wait for a trip to Jaycar to get some bits and bobs. I'm going to make a little circuit with a lamp in it to discharge the caps with.

Very carefully removed the board so some more pics. Some definite discolouration in one spot.....

[dave.king1]

Some definite discolouration in one spot.....

You'd almost describe that as a guilty blush.

Looking at the circuit you previously linked that had a solid state power circuit I suspect this will probably be very similar, why re-engineer what you don't have to

[BigDaddy]

Now you have that board out, you can check continuity of the power transformer windings with the multimeter. Look at both the primary and secondary sides. If the switch was working and the fuses are fine, the transformer is the next thing in line. Primary first (should directly connect to the switch), then secondaries which will connect to the board near those big caps and that bridge rectifying diode (BD1). Looks like they connect via molex plugs. You can do this b4 you discharge the caps as they are not connected to the tranny.

[BigDaddy]

Another way you can discharge the caps is with the multimeter. Select high voltage DC (>600vdc), hook one leg of a 1K resistor (1w) to the positive lead on the meter. Touch the neg lead to ground and the free leg of the resistor to the cap positive. Doing ut this way both discharges the cap and shows you viabthe meter if there is any voltage present. I modded a cheap meter for this process with a couple of banana sockets. Works a treat.

I’ve got a pic of mine on my phone but can’t seem to attach it! I don’t use image hosting so I could try PM or something