As per the thread title, if anyone has a legible schematic they can send me, I'd really appreciate it. If you PM me I'll provide my direct email address.
Many thanks,
Tom D.
Many thanks,
Tom D.
Help: I need a schematic for a Knight KN735 integrated EL84/6BQ5 PP amp
- Thread starter Wharfcreek
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FlaCharlie
Super Member
Here you go Tom, in pdf which can be enlarged to show detail.
Once again to my rescue! Many thanks Fl Ch! I really appreciate it. Hopefully it will be a relatively quick resurrection without too much in the way of repair necessary. It's in pretty sad shape, cracked knobs, a badly blemished face plate, a cabinet that will need to be stripped, sanded, and repainted, and of course, an 'amp' section that looks terrible! The PT in this is essentially solid rust! Hopefully it's not burnt out. But, I feel like starting a project like this without a schematic is like starting with one hand tied behind my back! So, again.....many thanks!! Tom D.
FlaCharlie
Super Member
Sounds like a serious undertaking. Please post some before and after pics.
Yes. For the 735 Knight used the circuit from their KN-728b. The layouts are different. The PEC components are included on that schematic. I might be able to dig that one up.
The 735 is a 728b circuit built on a Grommes chassis. Most Knights have the power tubes running horizontally out the back; the 735 mounts all tubes vertically.
https://audiokarma.org/forums/index.php?attachments/kn728b-jpg.138227/
The 735 is a 728b circuit built on a Grommes chassis. Most Knights have the power tubes running horizontally out the back; the 735 mounts all tubes vertically.
https://audiokarma.org/forums/index.php?attachments/kn728b-jpg.138227/
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FlaCharlie
Super Member
Great info.
For some reason the link didn't work for me. I was able to find it doing a search but it's pretty blurry.
Here's the full Sams in pdf, which can be enlarged to show detail.
Oh yeah, that is much better. Thanks.
i was wrong about the layout on the 728b; the tubes are vertical. Maybe that is the difference between 728 and 728b.
Wharf, this is similar to the Sams servicer for KN-735 ..... with much more info.
The oddest thing about these amps, to me, is the resistance between the screen supply and the cathodes. Those two 100K resistors. Anyone who knows, please chime in.
i was wrong about the layout on the 728b; the tubes are vertical. Maybe that is the difference between 728 and 728b.
Wharf, this is similar to the Sams servicer for KN-735 ..... with much more info.
The oddest thing about these amps, to me, is the resistance between the screen supply and the cathodes. Those two 100K resistors. Anyone who knows, please chime in.
parallel 100k so 50k effectively, but I don't really see the point. The ground side is 100 ohms, so its not like its going to bias up the cathode by enough to make any difference. Could simply be there as a bleeder resistor arrangement. Add some load to the power supply so the screen supply voltage doesn't swing around quite so much when the screens pull more current at high output, and it will discharge the caps after being turned off. Why they'd tie it to the cathode instead of ground I don't honestly understand.
OK, sorry for my delay in responding here, but 'family' events crowding my day! Anyway......first, thanks for all the great info!! This is about as helpful as it gets! I don't know if the PECs on my unit are 'in spec'....or even close. But, the good news on that is that I'm not too concerned about the RIAA stuff. The amp will most likely never see anything other than a CD player, or maybe an input from a laptop.
Funny about the reference to the Grommes units. Mine actually had 3 old Black-plate Grommes branded 12AX7s still in it. Sadly, all pretty well shot. But, still.... may be a little life left in 'em for something.
As to those 2 100K resistors....... I'm with you on that!???? WTF? That whole circuit appears to go back to the center tap on the filament winding. No 'direct' connection to 'ground' other than through the cathode resistor? Seems to me that whole circuit might be 'amended' some and it wouldn't necessarily hurt anything. But, I don't get that either!!
I will post a few pics of this old thing tomorrow.
Thanks to all of you for kicking in on this!!
Tom
Funny about the reference to the Grommes units. Mine actually had 3 old Black-plate Grommes branded 12AX7s still in it. Sadly, all pretty well shot. But, still.... may be a little life left in 'em for something.
As to those 2 100K resistors....... I'm with you on that!???? WTF? That whole circuit appears to go back to the center tap on the filament winding. No 'direct' connection to 'ground' other than through the cathode resistor? Seems to me that whole circuit might be 'amended' some and it wouldn't necessarily hurt anything. But, I don't get that either!!
I will post a few pics of this old thing tomorrow.
Thanks to all of you for kicking in on this!!
Tom
