A small issue with my '74 DR103

[Analog103]

I have this '74 DR103 which has been working great but there's a little problem with it. It's been going on for a while but now I decided to sort it out. Sometimes when I turn it on the pilot light goes on and then off immediately. Same happens when I have it running and put it on standby. Both happens occasionally. I was afraid to run any singal through it when this happens so I always turned it off completely and then turned it on again.

Do you think it's the switches? They're old, that's for sure. Can I clean them or do I have to buy new ones? Or could it be the pilot light? Or anything more serious like the power tranny or something?

I'm also not sure I run the rigth value fuses in there. What's recommended for 245V mains voltage?

Here's a short clip I made using my cellphone:

http://www.youtube.com/watch?v=1nxkxS5kl9I

I'm also waiting for some xf2 EL34's to change the JJ EL34's I have in now so I really want to sort this out.

[OldSchoolDave]

Sometimes when I turn it on the pilot light goes on and then off immediately. Same happens when I have it running and put it on standby. Both happens occasionally.

Quick question (I don't get to youtube very often...): Is it just the pilot light that cuts off? That is, does the amp continue to work when the light goes out?

Dave

[mhuss]

If the amp is working normally otherwise, it's likely the indicator itself.

The indicator lamp is a neon, and these eventually wear out. Unlike a conventional incandescent lamp, when neons start to fail they don't light at all intermittently, or start and then go out shortly afterwards (again, intermittently at first).

Unfortunately, these are harder to find than just about any other vintage Hiwatt part. If you are good with handiwork, it is possible to very carefully cut open the old indicator and replace the neon bulb inside, but this is not for the faint-hearted!

--mark

[Analog103]

I should try playing the amp when it happens next time.

But right now I remembered, that there was a loud brum from the amp when it happened. Does that rule out the indicator?

[Analog103]

I went to play the Hiwatt and it happened again with the mains switch when turning it on. I then turned on the standby switch (still no light) and there was nothing. Turned it off and then on again and there was sound. I then was turning the standby switch off/on for a while and it was normal all the time. But I'm pretty sure I remember the stand by switch to cut out as well.

Should I try and clean both switches with contact cleaner (I suppose WD40 isn't recommemded)?

Please note that this has happened in other places as well not just in my music room.

I'd still like to know the correct fuse values for Europe for a DR103 (my mains switch is set at 245V)!

Thanks!

[OldSchoolDave]

Regarding fuses: http://hiwatt.org/tech.html

It's sounding more like a failing switch (or switches) at this point. You could try contact cleaner (NOT WD40), but my guess is there's a physical issue that cleaning won't fix. You should also check the wiring to make sure nothing has broken loose. Here's what it ought to look like inside:

Switch Wiring 001.jpg (297.41 KiB) Viewed 1782 times

If the wiring is solid, it might be time to replace both Mains and Standby switches. Be sure to save the original nuts - they'll look better and save you a little bit of $.

Dave

[mhuss]

Yes, if the switch is shot, just exercising it or vibration can cause it to kick in sometimes. Toggle switches fail after long enough service. I would replace both, just so they match, for appearance sake.

--mark