AKG solid tube PSU failure !

[MartyMart]

Anyone have any experience with this PSU ?
It belongs to a friend and is blowing the fuse constantly, the PAIN is that to get
to the bottom of the board you almost have to destroy the case as all the
sockets are mounted and protrude over the board and are riveted onto the
case from the outside !!
Not a screw in sight !

ANy known issues / tips are very welcome.
It's very hard to test out and even look at the traces until it's all out of this
stupid case.

MM.

 

[mrclunk]

i repaired one for a mate a while ago, i think there's a know problem with the power transformer, i had to buy a new one.
i should still have the details at the studio somewhere, i'll have a look tomorrow.

 

[MartyMart]

Thanks that would be great, I wondered if it was the traffo as there's no
obvious signs of any other component damage, it's a quite cheap looking
grey lump and PCB mount too, which seems odd !!

Cheers,
Marty.

 

[rodabod]

Check the obvious things frist; shorts from HT and heater to ground.

If you suspect the power trafo, lift the secondary and see if it still blows fuses.

Roddy

 

[mrclunk]

found some old emails with stuff about the fix.

It had blown the protection VDR's, the inductor and the transformer was cooked.
The dodgy transformer was grey, the new improved is brown.

i ordered the bits from Cimple spares

2 x 0012 E 0038 ( 130V version) RV1 /RV2
1 x 0022 E 0036 Transformer ( brown housing ) TR1
1 x 0023 E 0089 533mH coil, L1.

also in an email from an AKG repair guy:
'Please note, the fuse rating on the power supply was later revised to
T200mA.'

think the schematics on the akg site.

 

[MartyMart]

Thanks chaps, great stuff - let me see if I can get that stupid case apart !!

MM.

 

[mrclunk]

heres the service doc

http://www.akg.com/mediendatenbank2/psfile/datei/37/solidtube4055d251a2cd0.pdf

 

[MartyMart]

Thanks, I did find it on the AKG site, do you have any idea of the cost of those
replacement parts ?
I need to give my mate an idea before I go ahead and repair it.

Many thanks for your assistance,

Marty.

 

[mrclunk]

cost me £48.56

 

[mikeyB]

[quote author="mrclunk"]cost me £48.56[/quote] :shock:

Whoa there :!:

Get in touch with www.saturn-sound.com. I've fixed 3 solidtubes - all psu faliure (transformer). It's a while since - but each tx cost £25 shipped to Manchester.
He's called Ashley Styles - a very nice man - very helpful - and some nice bits to sell also!
Hope this helps.

 

[MartyMart]

Mikey, that's a price for the Traffo, coil and RV1&2 so the traffo alone is
probably around the £25 area.
I get a dead link from the saturn site BTW

Marty.

 

[Sorr]

In the end I rebuilt it in a new case with a new (non AKG) transformer.
This is after I rebuilt the microphone and repaired the PSU twice!
Isnt there some comment about Harmon around this forum?

 

[mikeyB]

[quote author="MartyMart"]Mikey, that's a price for the Traffo, coil and RV1&2 so the traffo alone is
probably around the £25 area.
I get a dead link from the saturn site BTW

Marty.[/quote]

Sorry Marty - put . after com - try
www.saturn-sound.com

Should work

Only the traffo was fooked in the 3 I fixed. Just had one I fixed back on the bench - the mic cable had been broken! - fixed it and still going strong.

Mike

 

[barney]

+1 for replacing the psu transformer. AKG distributor had them in stock which made me think this was more than a one off. Hope I don't see it back on the bench too soon.

 

[MartyMart]

OK, well he's decided to have AKG fix it for £90 including VAT and the
postage in/out so that's not a bad deal and saves me "futzing" with that
stupid case for an hour or two !!
There would have only been £20 in it for me anyway.
Thanks for all the helpful links etc guys.

MM.

 

[Rob Flinn]

I have one of these on the bench at the moment, doing what you describe.  Initially it was obvious that the varistors had gone, which I replaced, gave it back to it's owner, it was fine for 8 hours, but then started blowing the fuses again.  I replaced the varistors again & same thing happened, all fine for several hours then pop !

The PSU has the grey mains transformer.

Does this sound like what the problem was for you guys ?    Time to replace the mains transformer ???

 

[mrclunk]

Defo. Replacement transformer i'm afraid.