This is Peter. The two Altec amplifiers I've got on the thread came from a drive in cinema in the U.S.A, they have 2X 811A output tubes in push pull plus 2X 816 rectifier tubes and they are zero bias.
These amplifiers need two new input transformers that feed the 811A tubes, I will be grateful if any body could let me know what the spec of the transformers would have to be to use a pre-amplifier with these altec amplifiers.
A friend purchased these Altecs off ebay thank you
These amplifiers need two new input transformers that feed the 811A tubes, I will be grateful if any body could let me know what the spec of the transformers would have to be to use a pre-amplifier with these altec amplifiers.
A friend purchased these Altecs off ebay thank you
Sounds like 1570Bs.
Four rectifier tubes?
If not, post an image?
Make sure they have not just the 70volt output.
That's a 1570BT. Ng.
The 1570 does not require any input transformer.
Download the schematic. The high-Z input will go to the spot where the transformer would normally feed. The rear apron has a small barrier strip with screw terminals, a pair of them go direct to the correct input.
I usually have put a hole next to that spot and put an RCA in it, direct connection.
Remove the HF comp capacitor from the feedback circuit completely, the amp will sound better.
Replace the coupling caps - the old ones tend to leak.
Do not change the value of the main B+ filter cap, it's a tuned circuit with the choke.
_-_-bear
Four rectifier tubes?
If not, post an image?
Make sure they have not just the 70volt output.
That's a 1570BT. Ng.
The 1570 does not require any input transformer.
Download the schematic. The high-Z input will go to the spot where the transformer would normally feed. The rear apron has a small barrier strip with screw terminals, a pair of them go direct to the correct input.
I usually have put a hole next to that spot and put an RCA in it, direct connection.
Remove the HF comp capacitor from the feedback circuit completely, the amp will sound better.
Replace the coupling caps - the old ones tend to leak.
Do not change the value of the main B+ filter cap, it's a tuned circuit with the choke.
_-_-bear
Ok, so no jpegs.
How about more info about it then?
Are there any markings at all on the chassis??
Model # evident?
Any silkscreening labels? Color?
Size or designation on the output transformer??
How about you take a look online at some 1570b photos and tell us how much it differs in layout and look.
Also try to find a 1570a or non-"A" layout which is different than the B.
They may well be homebrewed based on an Altec design??
_-_-bear
How about more info about it then?
Are there any markings at all on the chassis??
Model # evident?
Any silkscreening labels? Color?
Size or designation on the output transformer??
How about you take a look online at some 1570b photos and tell us how much it differs in layout and look.
Also try to find a 1570a or non-"A" layout which is different than the B.
They may well be homebrewed based on an Altec design??
_-_-bear
From the pictures I received some of the transformers look like Peerless. It is NOT a 1570 vintage amplifier as the composition and layout are not anything like a 1570. It is starting to look like someone used the Altec buzz word to push these puppies on ebay for a quick sale. They aren't even close to anything Altec built in that era. They look more like an RCA product.
Altec did make amps like you describe. The type 287W is described in VTV issue 9. That amp consists of two 805 triodes, two 866A rectifiers, five transformers and not much else. I guess your amp could be similar.
If it is, it may be just a booster amp. The 287W is at least. So you may need a power amp to drive it.
The schematic of the 287W is in the magazine - a quick web search didn't turn up anything.
Best regards,
Mikkel C. Simonsen
If it is, it may be just a booster amp. The 287W is at least. So you may need a power amp to drive it.
The schematic of the 287W is in the magazine - a quick web search didn't turn up anything.
Best regards,
Mikkel C. Simonsen
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