HEEEELLLLPPPP!! Croft mono problem

[Bigbird]

Hi all , ive got an issue with my right Croft 7r monoblock .

Ive just got out the shower to realise that no sound was coming through the right speaker but it was fine earlier .
After playing around with the cables ,with no results , i opened up the mono to find that the input valve(12bh7) was not glowing but the others were. (Pictured)

I thought one of my newest valves may have blown so i switched back in my old spares but still there is no glowing from them either and still no sound in right chanel .

Im wondering wether something has blown? Seems odd as they were only serviced and upgraded about 9-10 months ago.

I have noticed occasionally and intermittently (maybe 5-6 times) since i bought them a few months back, that this mono doesnt always fire up properly . It has soft start to allow the valves to warm up ,then the power light on the front panel turns from red to green after a few minutes to signal its ready. Sometimes the light would stay red and not click to green after long periods and i would have to switch it off and back on before it would play ball.

Im wondering if its an issue thats reared its head or im just unlucky and something has blown?? I cant see anything with any damage inside though and they have not been moved once since i set them up apart from opening the top up to carefully remove the input valves for newer ones.

Any help or knowledge would be great. Hopefully i dont have to send them back to Glenn in the UK

Cheers

Karl


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[AJSki2fly]

Hi Karl

I had a similar problem with one of my mono blocks (not Croft) this was caused by a failed capacitor on the heater circuit the valve. I think it will be a matter of getting it checked over and fixed, especially if it has been problematic from day one. It should not be too costly to fix just a pain sending it back.

[Bigbird]

Hi Karl

I had a similar problem with one of my mono blocks (not Croft) this was caused by a failed capacitor on the heater circuit the valve. I think it will be a matter of getting it checked over and fixed, especially if it has been problematic from day one. It should not be too costly to fix just a pain sending it back.

Thanks for the reply mate. I had a feeling it would be something like that. I do know a guy here in Oz that services Audio research and Macintosh amps so im thinking he may be able to work it out, but it would obviously be best for Glenn to do it . The shipping alone would be about 80 quid each way , plus the repair costs, so it starts getting expensive which is making me consider the guy i know here.


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[eksiil]

I had a similar issue with the warm-up circuit. contacted Glenn about repairs who said it was OK having it done locally (Estonia in my case, the other end of Europe). which is what I did. however, my 12bh7's were not playing up. I've gone through a fair number of fuses over the years, but it's been worth it.

good luck with getting your amp sorted.

[Opti-cal]

If sending to Glenn maybe best to wait until the Ashes are (nearly) over ey cobber . . .

[Audio Al]

Why not send it back to Glen Croft ?

[Firebottle]

Hi Karl, I don't think it will be a big job, or complicated to fix. Normally with Croft amps, certainly preamps, Glenn uses a 12V regulator and wires two 6V heaters in series.

To confirm look for a regulator chip marked 7812 bolted to the bottom of the case at the power supply end.
This may not be the case with the 7r, it may have 6V AC heaters direct from mains transformer.

Have you tried the valve from the other mono to check it's not the valve?
Have a careful look at the wiring on the valve base to see if there is a dry joint.

Post a pic on here if that helps.

[Macca]

Why not send it back to Glen Croft ?

From Australia?

Not a complex fix so I'd have thought any competent EE would have no issues with sorting it, shipping it all the way back here to be fixed would be nuts.

[Bigbird]

Hi guys thanks for the replies. As already expressed ive moved to Oz so sending it back is the last thing i wanna do really. Ive already emailed Glenn a few times over the past few months to talk about possible updates and valves but never had a reply so maybe i have the wrong email (glenn@croftacoustics.co.uk)???
Alan ive tried a couple of valves and theyre all the same result. Heres a few pics of the inside. No evidence of solder issues that i can see. Maybe one of you can point me to the area i need to be.


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[Bigbird]

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