Low voltages under load from PSU equal bad PT?

[audiopete]

I have a Vox AD15VT that seems to power up but doesn't work. Power LED comes up dim. The digital section does not respond and no LEDs illuminate. I measured PSU voltages and they are all low. About +-10VDC for the +-15VDC supply and 2.2V for the 3.3V digital supply. This is with preamp board disconnected. There's no DC rectification for filament supply but the AC reads 3.4VAC. This would be low for a tube heater and seems to indicate bad heater winding.

It doesn't matter if I just plug in one set of secondaries, the DC voltages are low regardless of which supply is plugged in.

http://www.valvetronix.net/docs/AD15...vicemanual.pdf

PT unloaded:

3.5VAC on filament taps
19VAC on +-15VDC supply taps
3.2VAC on +3.3VDC digital supply taps

Would you agree the heater winding is bad and pulling down all voltages?

[g1]

Does it have one of those crazy fuse holders that changes it over to 240V operation if it's turned upside down?

[audiopete]

Ha ha well I just looked at the rear panel to check that and what do I see printed? "220V-230V 50Hz"

So worse than that, G-One, it's an import that wants 220V. That would do it.

Man it's one of those days I think. Thanks G-One!

[Chuck H]

Gotta love how IEC plugs make things simpler

[audiopete]

I spoke to the owner and he bought it used and it never worked. Funny thing is if I had gone and ordered a PT, it would have fixed the amp and I may have never known the true problem. He is going to use it with a step up xformer.

[audiopete]

Actually I found out a replacement 120VAC PT from Jam Industries is $12.12 so the owner wants to swap it out.

[g1]

That's crazy! From Jam? Forgive me for being skeptical but I'll wait til you have it in your hand.

[audiopete]

I know. I am calling in this morning with payment info so I will confirm with them it is indeed the correct part. I emailed them the part number right from the service manual and that's the quote I got.

[audiopete]

Transformer ordered from Jam - $12.12 plus $9.95 shipping. Crazy.

[J M Fahey]

Straight part number ordering can be tricky, because numbers are assigned at random ... or to be precise using a system which looks "logic" ... to them.
Plus there's always the possibilty of a typo.

I *hope* you get an around 2 or 3 pounds power transformer for an AD15VT , and pray they don't actually send something like:



Not being cynical, at all, but the low price surprises me and a similar thing has already happened to me.

Oh well, wish you the best

[audiopete]

Oh I know, I will believe it when it arrives I'll update.

I got the part number from the service manual and actually it's the same part number for Canadian, US and Export 117VAC inputs.

Page 7 - http://www.valvetronix.net/docs/AD15...vicemanual.pdf

[J M Fahey]

Oh I know, I will believe it when it arrives I'll update.

I got the part number from the service manual and actually it's the same part number for Canadian, US and Export 117VAC inputs.

Page 7 - http://www.valvetronix.net/docs/AD15...vicemanual.pdf

Well, the price is incredibly good

Personally I'd buy as many as I could to build hybrid 15W amps, no kidding.

I guess they bought 1500 transformers 5 years ago and still have 1487 unsold units left.
That would explain the fire sale price.

[g1]

Also, some times they just make errors in pricing. Very rare that they work out in your favour though. If so, someone will probably notice and the next guy will have to pay the real price.

[audiopete]

Like the Cascade Fathead II with Lundahl transformer I bought for the price of the regular old Fathead....yay internet pricing errors!

BTW JM, only 1 piece in stock I got the last one from JAm anyways.

[J M Fahey]

Ouch, you were very lucky then.

I'll change my scenario to: "thanks God somebody bought the one which had been collecting dust for 5 years"

"Now we can clean the shelf and use it for something else"

or something like that