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Peavey Classic 400 - Mega Thread - Part II

#261
I'd have to scan my PM folder, but I traded several messages with Bobby about modifications and such the first time I owned one of these.

IIRC, he said that he set bias for the Classic 400 in his office using a 'scope. That tends to give a fairly "hot" bias, and given 675 vdc on the plates, I want to run them more conservatively than that...but not cold.
 
#262
Here's what Bobby said (like 10 years ago in Part I of the MegaThread):

"The bias voltage depends on the tubes, so I can't really tell you what voltage to set it at. If you increase the bias you will warm up the tubes more, I don't know about the tone."
 
#263
And here's a PM from Bobby going into more depth on the topic:
"I have a lot of tubes at my disposal, so when I bias a personal amp I tend to go for as clean of an output as possible, so I may use a scope only.
This way is not always the best for tube life, but is not necessarily bad.
For products that I work on, I have to come upwith an ideal bias point, so I go with plate current in addition to using a scope."
 
#267
I can see why someone would NOT want to bias this amp using the transformer shunt method -- talk about "not fun"!

But IIRC, when I retubed with KT-88s and set the bias voltage at Peavey's -52v spec, my bias current was somewhere around 18 mA -- so that's why I stopped using that method.

It seemed to only apply to the stock tubes.
 
#268
20160425_193207.jpg



So this happened.
 
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#270
One of these beast is currently for sale here in Japan for what seems to be a decent price. I'm very tempted but reluctant because of the supply transformer. We have 100VAC grid voltage here in Japan, but I will very likely return to Europe next year where my stuff needs to operate on 230VAC. No problem for most amps as it's quite common for the power transformers to have multiple coil taps on the primary side which can be rewired for different supply voltages (did this before on Mesa/Boogie, Ampeg and Genz Benz amps).

But... after checking the schematics that were kindly provided here, it seems that Peavey installed different transformers for different markets (I found the same on some SWR and Marshall Amps). So it's probably not possible to rewire this amp from 100VAC to 230VAC. Which would be a shame... And changing the transformer (if I can actually find one) is just not feasible I guess...

Can any Classic 400 owners comment on this? Any chance that someone has checked their power supply inside the amp (i.e. transformer primary windings) and could either confirm or disprove what the schematics say?

Unfortunately the seller is not close to my city at all, so I can't just go and take a look at the wiring...

Thanks a lot!
 
#271
The power transformer on the Classic 400 clocks in at over 40 lbs all by itself, so I can see why they didn't build it with any extra windings to provide additional voltage taps.

Not sure if the Japan/Euro model shared a transformer, and my schematics are at home -- but our resident Peavey amps expert would be able to give you the definitive answer on that...

So, paging @BbbyBld

KuroiEvo said:
One of these beast is currently for sale here in Japan for what seems to be a decent price. I'm very tempted but reluctant because of the supply transformer. We have 100VAC grid voltage here in Japan, but I will very likely return to Europe next year where my stuff needs to operate on 230VAC. No problem for most amps as it's quite common for the power transformers to have multiple coil taps on the primary side which can be rewired for different supply voltages (did this before on Mesa/Boogie, Ampeg and Genz Benz amps).

But... after checking the schematics that were kindly provided here, it seems that Peavey installed different transformers for different markets (I found the same on some SWR and Marshall Amps). So it's probably not possible to rewire this amp from 100VAC to 230VAC. Which would be a shame... And changing the transformer (if I can actually find one) is just not feasible I guess...

Can any Classic 400 owners comment on this? Any chance that someone has checked their power supply inside the amp (i.e. transformer primary windings) and could either confirm or disprove what the schematics say?

Unfortunately the seller is not close to my city at all, so I can't just go and take a look at the wiring...

Thanks a lot!
Click to expand...
 
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#277
I scored a black rat fur 400 today. The DDT is disconnected, the fan is noisy and there's no footswitch. But I am happy so far.

Anyone have a part number for a fan replacement?
 
#278
cornfarmer said:
I scored a black rat fur 400 today. The DDT is disconnected, the fan is noisy and there's no footswitch. But I am happy so far.

Anyone have a part number for a fan replacement?
Click to expand...
I got it from a VERY reliable source that the fan is unnecessary and disconnecting it will save you vibration.

You can remove it altogether for some weight savings too...
 
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