Hi!
I got this amp from a friend about a year or so ago. The guy who had it originally was a projectionist and has/had a lot of old cinema gear. I don't know what happened but he decided this amplifier and some other things were rubbish, so he threw the valves in the bin and the chassis on the scrap heap. Fortunately my friend rescued it, but he didn't find the valves.
Underneath, it has AE285 stamped on it. Some research suggests this might be a Westrex model number. I can't find anything further information about them. Anyone care to enlighten me? There are a few variable resistors underneath. I'm wondering what would be the best way to adjust them. I think one is a bias control and the other is a mains hum balance. Also, I don't know what the output impedance is on the output transformer.
I bought some cheap 6L6's and replacement 6SJ7's to see if the thing worked, and put a higher value 20W cathode resistor on the output stage to suit the new tubes. It works really well! I won't be leaving it like this...
Looking around the Googles for this sort of thing shows it might be quite valuable. Therefore I'll be investing in some real KT66's and I'll set it up with some decent speakers. I'm not letting it out of my sight, in case someone wants to dismantle it for parts to make their own amp, or worse, to sell off the components individually!
Thanks
Alexis K.
I got this amp from a friend about a year or so ago. The guy who had it originally was a projectionist and has/had a lot of old cinema gear. I don't know what happened but he decided this amplifier and some other things were rubbish, so he threw the valves in the bin and the chassis on the scrap heap. Fortunately my friend rescued it, but he didn't find the valves.
Underneath, it has AE285 stamped on it. Some research suggests this might be a Westrex model number. I can't find anything further information about them. Anyone care to enlighten me? There are a few variable resistors underneath. I'm wondering what would be the best way to adjust them. I think one is a bias control and the other is a mains hum balance. Also, I don't know what the output impedance is on the output transformer.
I bought some cheap 6L6's and replacement 6SJ7's to see if the thing worked, and put a higher value 20W cathode resistor on the output stage to suit the new tubes. It works really well! I won't be leaving it like this...
Looking around the Googles for this sort of thing shows it might be quite valuable. Therefore I'll be investing in some real KT66's and I'll set it up with some decent speakers. I'm not letting it out of my sight, in case someone wants to dismantle it for parts to make their own amp, or worse, to sell off the components individually!
Thanks
Alexis K.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
i have some circuits for these amps and how to wire the output transformers for different speaker's Ohms.
I made the mistake of rebuilding them; the out put transformers can not handle Much feedback from the out put best to stick to the circuit and use feedback from the plates to the drivers. Have very good Bass.
I can scan the circuits if you wish.
Phil
I made the mistake of rebuilding them; the out put transformers can not handle Much feedback from the out put best to stick to the circuit and use feedback from the plates to the drivers. Have very good Bass.
I can scan the circuits if you wish.
Phil
I have no idea what kind of amp that is, but the receiver underneath it I am familiar with... My parents have one just like it that they still use. It looks like yours is still working also. 🙂
For my own reference, and if anyone's curious about the topology of this thing, I reverse engineered the circuit. It uses a transformer phase splitter right at the beginning.
Yea! It's a Realistic STA-84. It sounds great.
An externally hosted image should be here but it was not working when we last tested it.
Yea! It's a Realistic STA-84. It sounds great.
Nice.
But there's no decoupling cap for the driver tubes' screen grids after 330KΩ?
Can you explain the benefit of not having the screen grids decoupled in the schematic, extra feedback? Just curious.
Thanks Phil! I can see there are some differences between the AE293 and the AE285, but the important information is there.
Thanks again,
Alexis K.
Thanks again,
Alexis K.
Ive been trying to track down a circuit diagram for a Westrex AE285 KT66 cinema amplifier would someone be able to send it to me. Thanks
Would it be possible to see the circuit for AE285. I have a couple with me and would like to do it up. They have not worked for about 30 years!!