Yarland 34A - Crunch sound, now not the same, any ideas?

[jolon]

Hi,

My Yarland 34A made a crunching sound, I turned it off then back on and all I got was static. I thought it was gone, but when I tried again the next morning it seemed fine. However after about a week I realised it just wasn't the same as previously. Piano notes sound a little off and it lacks the life it used to have.

I've opened it up and nothing seems blown. I've also changed both the driver and output tubes but it still sounds the same.

Any ideas?

Thanks,

Jolon.

[Miles Prower]

Could be a coupling capacitor is going bad on you.

[jolon]

Thanks, I might give the coupling capacitors a go.

However, it seems to affect both channels, if one coupling capacitor goes could it affect both channels?

Thanks,

Jolon.

[Brit01]

However, it seems to affect both channels, if one coupling capacitor goes could it affect both channels?

No it shouldn't. There will be a coupling cap for each channel.

You have the schematic handy?

[jolon]

Originally Posted by Brit01

No it shouldn't. There will be a coupling cap for each channel.

You have the schematic handy?

The only schematic I have found is this:

http://www.petemoore.pwp.blueyonder....udio/FV34A.jpg

But there are some differences with the FV34A-III I have.

The PSU may be similar to the one in the FV34C:

Yarland 34 ciii amp

My initial thought was that it was in the PSU, may be too much current. Could it be one of the rectifier diodes?

[Svein_B]

You should check all voltages.
It could be a problem with the high voltage or bias supply.

SveinB

[jolon]

Originally Posted by Svein_B

You should check all voltages.
It could be a problem with the high voltage or bias supply.

SveinB

I've never checked voltages on a valve amp. What is the best way to do it?

Should I leave the tubes in, or have the tubes out and place the multimeter probes in the sockets?

Thanks.

[spkr guy]

Is it made in China? if so start replacing all internal parts until it sound right.
I once got a deal on 5 for the price of 1 chinese amps SS and tube all but one blew something inside and the one that still works goes dead after warming up 5 mins.

[jolon]

Originally Posted by spkr guy

Is it made in China?

It is, however Yarland are a bit better than the typical e-bay brands. Having said that, I didn't pick mine up through the proper channels but got mine off an Australian auction site, so I can't verify the quality. It did come with a factory warranty but I converted it to triode earlier in the year which would have voided the warranty (I converted it back to pentode because I thought it sounded better).

if so start replacing all internal parts until it sound right.

I was thinking of doing that, I'm just looking for a good place to start. I've ordered an AMP-HEAD Dual BiasTester-MPD Probe to check the bias and plate voltage.

I once got a deal on 5 for the price of 1 chinese amps SS and tube all but one blew something inside and the one that still works goes dead after warming up 5 mins.

lol