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-   -   Pre3 problem. (http://www.world-designs.co.uk/forum/showthread.php?t=6889)

pre65 14th September 2013 03:09 PM

Pre3 problem.
 
My Pre3 has a problem.:(

I have a noise on one channel, it's regular, but intermittent. I say intermittent but the gaps between are very small. A bit like motorboating but not.:confused:

When the noise appears (seems to need a little while to start) the volume control (shunted alps) and selector switch have no effect, even mute.

I did change the two 0.1uf coupling caps but that made no difference.

Help.:o

Richard 14th September 2013 05:05 PM

Re: Pre3 problem.
 
Hi Philip,

Sounds like a noisy valve, have you swapped them over to check or popped in a new one?

Pre3 runs them quite hard compared with a lot of other gear (several whole mA!) and Gerry B and I have both had noisy ECC82, the supplied JJs in particular.

I think they would be fine in gentler applications but perhaps the extra heat gets to them. We made up a good pair between ours and that was fine and I use some nos Mazda/Thorn which are good and have been in 2 or 3 years now :thumbsup:

pre65 14th September 2013 07:54 PM

Re: Pre3 problem.
 
I did try swapping the two valves around but the noise stayed put.:(

I'll see if I can find the original valves and try them again.

pre65 14th September 2013 09:09 PM

Re: Pre3 problem.
 
I found the two ECC82 and plugged them in, and the noisy channel was noisy as soon as I switched on.:eek:

I wiggled the valve a bit and it's gone quiet for now. Will see how it responds after 30 mins or so.

I was using GE 5814wa up till today.:)

pre65 16th September 2013 05:39 PM

Re: Pre3 problem.
 
Touch wood ( puts finger on bonce ;)) the pre3 is still noise free.:thumbsup:

Richard 16th September 2013 05:46 PM

Re: Pre3 problem.
 
Great stuff, what do you think it was, noisy valve, dusty socket, or is it worth resoldering the bases to the pcb do you reckon?

pre65 16th September 2013 05:53 PM

Re: Pre3 problem.
 
I'm more inclined to blame the socket.

I re-soldered the valve bases a while ago when the problem first occurred.

Perhaps I will re-try the 5814wa at a later date.

Greg. 16th September 2013 10:19 PM

Re: Pre3 problem.
 
Glad you've got it sorted, our Philip :thumbsup:

pre65 17th September 2013 11:14 AM

Re: Pre3 problem.
 
Quote:

Originally Posted by Greg. (Post 80204)
Glad you've got it sorted, our Philip :thumbsup:

Cheers Greg.:)

I've tried several times to build a better pre-amp than pre3 but although I have had successes I always end up coming back to pre3.:cool:

Ali Tait 17th September 2013 06:15 PM

Re: Pre3 problem.
 
The Aikido not better then!

pre65 17th September 2013 10:20 PM

Re: Pre3 problem.
 
Quote:

Originally Posted by Ali Tait (Post 80212)
The Aikido not better then!

Not as I built.;)

BUT, I would think one built on the proper PCB might be ?:D

Ali Tait 17th September 2013 11:35 PM

Re: Pre3 problem.
 
Dunno, find out when mine gets here, it's still en route.

david 18th September 2013 01:11 PM

Re: Pre3 problem.
 
Depends on your ears (and ancillary components)! My Aikido with Charcrofts, Mundorf ZNs, and Mills resistors is very comfortably ahead of my modded Pre 3 (with TJS and similar mods). Before that the CF Pre I made with the right and left power supply decoupled also outperformed Pre 3. But Pre 3 is good, and has it's charm. My main issue that led me down the road was its too high gain and also that running its tubes full tilt you get quite a high hiss on the output, compared to silence with the modded CF and inky blackness with the Aikido.
David

Richard 18th September 2013 03:43 PM

Re: Pre3 problem.
 
Quote:

Originally Posted by pre65 (Post 80197)
I'm more inclined to blame the socket.

I re-soldered the valve bases a while ago when the problem first occurred.

Perhaps I will re-try the 5814wa at a later date.

Yes I've got 2 or 3 types of 5814 and various ECC82s but have never tried them in there, I got as far as the second ECC82 type and it was so good I just left them in! A tip on soldering pcb type valve bases if you don't already do it is to fit a valve to the socket first which then ensures the contacts are nicely aligned as otherwise they can float around a bit and may end up not contacting the pins so well.

pre65 20th July 2020 12:05 PM

Re: Pre3 problem.
 
I never really got to the bottom of this problem, and as a result Pre3 has sat, unloved, for many a year.:(

So, now I am going to get it sorted. I've asked Matthew to sell me a new PCB and two new valve bases.

I'll let you know how I get on.:)

pre65 28th July 2020 03:04 AM

Re: Pre3 problem.
 
Thanks to Matthew I now have the PCB and 2 valve bases.

I'm in the middle of refurbishing the 833a amps at the moment (one done so far) so I will wait till that job is completed before starting.:thumbsup:

pre65 26th September 2020 05:19 PM

Re: Pre3 problem.
 
I got bored today, so I took the PCB out of it's packing and inserted PCB pins in the relevant holes.

I've ordered the resistors (Takman) and 470uf caps (Elna Silmic 2) from HFC, and will use the Mundorf Mcap Evo that Bob gave me for the coupling caps.

pre65 26th September 2020 06:12 PM

Re: Pre3 problem.
 
Got a question on Pre3 PCB wiring.

I found my parts list but not the assembly instructions.

On my original build PCB positions OPR- and OPL- have PCB pins fitted, but no wires connected to them. Is that correct ?:confused:

Greg. 26th September 2020 06:18 PM

Re: Pre3 problem.
 
Do you want me to send you the instructions?

pre65 26th September 2020 06:23 PM

Re: Pre3 problem.
 
Quote:

Originally Posted by Greg. (Post 91718)
Do you want me to send you the instructions?

That would be nice Greg, postal of PDF via Email ?

Greg. 26th September 2020 06:34 PM

Re: Pre3 problem.
 
Iíll send it to you by email shortly.

pre65 30th September 2020 07:36 PM

Re: Pre3 problem.
 
Quote:

Originally Posted by pre65 (Post 91715)
I got bored today, so I took the PCB out of it's packing and inserted PCB pins in the relevant holes.

I've ordered the resistors (Takman) and 470uf caps (Elna Silmic 2) from HFC, and will use the Mundorf Mcap Evo that Bob gave me for the coupling caps.

I received my packet from HFC yesterday, so tonight I checked the items, everything OK. (as I expected)

However, the Elna Silmic leads are too big for the PCB holes. The leads measure 0.8mm, so I've just ordered an 0.85mm drill so as to make them fit.

This is not a criticism, just an observation.

Richard 30th September 2020 09:43 PM

Re: Pre3 problem.
 
Good info Philip a 1 or 1.5mm would be fine of course but just solder both sides if it's a through plated hole :thumbsup:

pre65 1st October 2020 03:26 PM

Re: Pre3 problem.
 
Quote:

Originally Posted by Richard (Post 91726)
Good info Philip a 1 or 1.5mm would be fine of course but just solder both sides if it's a through plated hole :thumbsup:

Thanks Richard. No through plating that I can discern.

I've populated the board as far as I can today, the drill should be here in a day or so.

bob orbell 1st October 2020 06:05 PM

Re: Pre3 problem.
 
Phillip, a small round needle file will do the job if you have one, use the pointed end and twist the file, but go in from the underside of the board so as to leave as much track as pos. Bob

pre65 1st October 2020 06:14 PM

Re: Pre3 problem.
 
Thanks Bob.

I realise that there were other options available, but as I'm not in a panic I'll wait for the drill.

If I could be arsed I'd spend hours searching for the 1mm drill bit I have probably got somewhere amongst all my belongings.:D


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