Tube amp questions

pmlewis

I recently dug out an old amp I go from a resale shop about 10 years ago. I never really tried it out other than turning it on. I was going to hook some speakers up to it but I am a little confused by the speaker hookups. There are two terminal strips on the back, one marked left and one marked right. There are a series of screws on each marked 0 4 8 16. I assume that these numbers would correspond the the impedence of the speakers I am using. Do I hook up the negative to the 0 and the positive to the number, or does it matter? Do I need to let the tubes warm up before I try the unit? I really know nothing about tube amps and any help would be appreciated.

Tour2ma

Not a name I recognize... but a cute little integrated amp.

You're correct on the meaning of the speaker terminal numbers. Many older amps, tube or SS, used this, e.g., Dynaco, Mcintosh.

Most probably the negative speaker lead is intended to go to the "zero" terminal, but that doesn't guarantee absolute phasing is preserved. Were you to swap wires, no harm done.

As for bringing up the unit...

Units with electrolytic capacitors, commonly used in older amps, that have been idle for long periods of time should be brought up on a Variac-type voltage regulator. Start at around 30 V and raise it 10 V every two to four hours, with longer times early in the process. This gradual increase in supply voltage "reforms" the electrolytic. Just cranking it up on a full 110 V current will damage the capacitor.

I cannot tell for sure whether that's an electrolytic (the cylinder in lower right of the pic with its top popped), but it looks like one to me. At any rate, if it's not, bringing it up on a variac isn't going to hurt it.

I would also recommend checking the tubes before power up. If one is bad, it could take other circuit elements with it.

Lastly, when you do power up, do it with speakers connected. Tube gear always likes/ needs to see a load when it is on. The volume should be dialed to near minimum.

One school also likes to have a continuous signal input active during the process, e.g., a tuner. As best I can tell, electronically this is not essential, but it does gives some positive feedback that the old piece is going to live again.... or not.

Good luck...

RuSsMaN

Just plug it in, turn it on. If it blows a cap or two, fix it. Variacs (I have one) really just prolong the inevitable. Sure, the caps can reform, but chances are they will be so far out of spec it's not going to sound good anyway. That being said, it appears to have already been worked on, that large grey cap is not original, someone has had it on their bench.

Looks like a neat little amp, single ended 6BQ5/EL84. Judging from the size of the output trannies, probably in the 3-5 watt range. If you feel like selling it, let me know.

Cheers,
Russ

pmlewis

Thanks for the replies. Since I don't have access to a variac I think I will take Rusman's suggestions and just let it rip. I don't think it's collectable or anything and I only have a few bucks in it. I should have some time over the 3 day weekend to play around with it so I'll let you know how it turns out.

Tour2ma

Yeah, we kind of covered the full range...

Good luck and let us know how it goes.