Phono Pre Amp Valve Issue?

[bob4333]

My vinyl replay which runs Cartridge - Phono Pre Amp - Power Amp, has dropped it's LH channel. RH is fine.

If I swap the RH / LH phono leads over at the Phono Pre Amp input there's still no LH channel so I deduce the cart is OK and the Phono Pre Amp has developed a fault.

Likewise, all is fine when inputting from the CD - Pre Amp (ARC LS27) - Power Amp. I therefore suspect the Icon Audio PS3 Mk 1 Phono Stage.

The only visual anomaly is that the 12AX 7EH (ECC83) Phono Power Supply valve barely glows in comparison to all of the others (8 in total). Power Supply Unit = 1x EZ80, 1x ECC83, 1x 5687: Pre-Amp = 4x ECC88, 1x 6SN7.

Would this be normal or is it a sign of failure? I'm assuming it's OK as this is in the Power Supply and would affect both channels rather than just the LH?

I'm going to swap the two pairs of ECC88's over in the pre amp to see if the problem moves. I can do continuity tests and measure voltages but that's about where my knowledge of electronics ends.

Anyone have any suggestions, or able to cast doubt on my logic, before I consider further steps which will probably involve throwing money at it?

[Firebottle]

Just throw money at me Bob, I think I am a bigger target.

Seriously, the '83 in the psu is OK as you still have one channel. With some '83 valves it is difficult to see the heater.
If you'd like to pop over I can give it the once over.

[Lawrence001]

You might as well try a couple of things first. Swap the phono out leads around and see if the problem swaps sides. If so, then look at swapping the valves around as you say. Although it could be the phono leads themselves, have you got another pair to try before messing around with the valves? Just use the ones from the CD player if not.

[bob4333]

You might as well try a couple of things first. Swap the phono out leads around and see if the problem swaps sides. If so, then look at swapping the valves around as you say. Although it could be the phono leads themselves, have you got another pair to try before messing around with the valves? Just use the ones from the CD player if not.

Can't fault the logic Lawrence and worth a try, although I'm hopeful rather than confident.

I have enough leads around to confuse the phono amp no end so one of them may work if that's the issue. I'll set some time aside to get swapping and see if it produces anything. Thanks for responding.


Just throw money at me Bob, I think I am a bigger target.

Seriously, the '83 in the psu is OK as you still have one channel. With some '83 valves it is difficult to see the heater.
If you'd like to pop over I can give it the once over.

Thanks Alan. If the messing around comes to nought I'll drop you a PM and start saving. This is a very early PS3 that was sent out on loan for magazine appraisal before being refurbed and sold off. I took it back to Icon in 2018 for overhaul and a re-valve but didn't like the ECC88's they put in, so replaced them with Tesla's which I found a bit warmer. Just for the "fun" of it I may try replacing all of the valves in the pre amp stage (I have a spare RCA 6SN7) and see what happens.

Anyway, here's a gratuitous pic of the little chap, all aglow but not the full five bob.


https://i.imgur.com/pC3SRKY.jpg

[bob4333]

This got a bit weird, but I think it's sorted now.

Taking Lawrence's route first I swapped over the pre amp outputs and bingo - back in business! Fixed it I thought and swapped them back, but when I came back later that evening for a bit of a listen it was back to square one with no LH channel.

Next day I removed the Tesla ECC88's and substituted a set of Siemens. Sound was fine, both channels singing and unexpectedly a massive uplift in performance compared with how the system sounded prior to the channel failure. The system was so quiet compared to the failed Teslas it definitely gave pause for thought. I've concluded that the added system noise should have been a warning that something was up. The channel failure just about confirmed it. A wiser man next time perhaps.

The Siemens sound pretty good, just needing the volume increasing slightly for the same listening level so I guess they're of a slightly lower output. But they're not as good as I remember the Tesla valves when new, so an order for some NOS E88CC Tesla Gold Pin's has been placed for delivery next week. Prices seem to have shot up and not so many outlets have any in stock now so I assume they're drying up. Plenty of JJ's though which I suppose is a comfort.

Icon quote ECC88 valve life in the PS3 of around 3000 hours. The 6SN7 and those in the power supply about twice that. I must have been using it more than I realised.

Assuming of course that I've found the problem............:doh: