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General Discussions => The Lab => Topic started by: MartyMart on June 30, 2008, 04:57:51 PM

Title: AKG solid tube PSU failure !
Post by: MartyMart on June 30, 2008, 04:57:51 PM
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.
Title: AKG solid tube PSU failure !
Post by: mrclunk on June 30, 2008, 05:31:54 PM
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.
Title: AKG solid tube PSU failure !
Post by: MartyMart on June 30, 2008, 05:38:06 PM
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.
Title: AKG solid tube PSU failure !
Post by: rodabod on June 30, 2008, 05:55:04 PM
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
Title: AKG solid tube PSU failure !
Post by: mrclunk on June 30, 2008, 05:55:36 PM
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.
Title: AKG solid tube PSU failure !
Post by: MartyMart on June 30, 2008, 06:47:08 PM
Thanks chaps, great stuff - let me see if I can get that stupid case apart !!

MM.
Title: AKG solid tube PSU failure !
Post by: mrclunk on July 01, 2008, 05:44:35 AM
heres the service doc

http://www.akg.com/mediendatenbank2/psfile/datei/37/solidtube4055d251a2cd0.pdf
Title: AKG solid tube PSU failure !
Post by: MartyMart on July 01, 2008, 05:47:05 AM
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.
Title: AKG solid tube PSU failure !
Post by: mrclunk on July 01, 2008, 06:00:43 AM
cost me £48.56
Title: AKG solid tube PSU failure !
Post by: mikeyB on July 01, 2008, 06:15:41 AM
Quote from: "mrclunk"
cost me £48.56
: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.
Title: AKG solid tube PSU failure !
Post by: MartyMart on July 01, 2008, 06:22:38 AM
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.
Title: AKG solid tube PSU failure !
Post by: Sorr on July 01, 2008, 06:33:16 AM
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?
Title: AKG solid tube PSU failure !
Post by: mikeyB on July 01, 2008, 09:13:01 AM
Quote from: "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.


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
Title: AKG solid tube PSU failure !
Post by: barney on July 01, 2008, 10:04:20 AM
+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.
Title: AKG solid tube PSU failure !
Post by: MartyMart on July 01, 2008, 11:58:43 AM
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.
Title: Re: AKG solid tube PSU failure !
Post by: Rob Flinn on September 30, 2009, 08:01:00 AM
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 ???
Title: Re: AKG solid tube PSU failure !
Post by: mrclunk on September 30, 2009, 08:24:15 AM
Defo. Replacement transformer i'm afraid.