Just completed my #183 clone, wa-hey!

[Neun elf]

Hi I have just completed building my #183 clone (not ceriatone) and it seems to work pretty well first time around.(Always a bit suspicious of that!!).
The only difference on mine from the published schematics, is that I have omitted the 25pF snubber caps on V2 as I could not find any 200v discs. I do get oscillation if the volume is turned up beyond 3:00 o'clock, with the master volume dimed. It appears on the top and wiper of the master volume pot, and seems to be about 2khz. Would fitting the snubbers cure that?

Thanks in advance for your help.

[boldaslove6789]

You might want to post a gut shot it may help us determine any problems you may be hearing.

[Neun elf]

I would be happy to, if I knew how!

[Neun elf]

I think I have it now.
Gutshots below.

[Colossal]

I would be happy to, if I knew how!

1) take relevant macro shots of your preamp board and overall shots showing the board and lead dress (don't post blurry photos)
2) plug digital camera into computer via USB
3) use your camera's software or iPhoto (or equivalent) to download photos from the camera
4) trim and scale photos as needed to remove useless or blurry information
5) export photos as .jpg or .png format (72-100dpi is fine)
6) reply to your post in this thread, click Choose File, find your photo files on your desktop. Click ADD ATTACHMENT after each photo. Wait till it uploads (patience). Repeat until all photos are in the queue and you can see their filenames in blue in files to attach to your post.
7) Click SUBMIT after all photos are uploaded.
8 ) Congratulate yourself with the consumption of cold ale.

Note: make sure photos are not 5MB each. Try to keep them around 500k-1M or so.

Good luck.

[catears]

I would warn against using those little bourns .5 watters and use something rated 1 watt for those trimmers on the OD and PI plates.

Always love dumbles with turrets- looks great!

[ampdork]

Those snubbers will buy you nothing for the stability issue your having. Sorry m8 wish the answer was that easy..

Looks like you have shielded your master? Shouldn't need that.

I;d look at losing that on the master and routing the OD and MV leads a little more "stock" and see what you get...

maybe better eyes then mine can see something else that is obvious.

[groovtubin]

Hi I have just completed building my #183 clone (not ceriatone) and it seems to work pretty well first time around.(Always a bit suspicious of that!!).
The only difference on mine from the published schematics, is that I have omitted the 25pF snubber caps on V2 as I could not find any 200v discs. I do get oscillation if the volume is turned up beyond 3:00 o'clock, with the master volume dimed. It appears on the top and wiper of the master volume pot, and seems to be about 2khz. Would fitting the snubbers cure that?

Thanks in advance for your help.

you power supply MAIN< resistor network looks a bit off, i run them from pos to pos, negative to negative, then run a wire from pos top, to negative, to ground

[Structo]

Hi Neun Elf,

Are you running EL34's?

If so you might want to try 1K-1K5 screen resistors.

I can't read your grid stoppers on the power tubes but 5K1-5K6 is the usual range.

[Neun elf]

Thanks for all your comments guys. I am running a pair of JJ/Tesla 6l6GC output valves with 5k1 grid stoppers, and while the PSU board layout may not be exactly as HAD did it, it is schematic correct including the correct ground points for each section. I will try to get an exact frequency for the oscillation, that may help give a clue. As I said it only occurs when all the volume controls are at maximum.

[Structo]

The solution is simple.

Don't do that!

[washburnmemphis]

Are you running your amp as a head or a combo?

[Structo]

Are you still having problems with this amp?

Jim at Omega amps (groovetubin) knows his stuff.

If I were you I would:

1) remove shielded cable from Master Volume and replace it with single wires, being mindful of lead dress and routing.

2) I can't tell what's going on with the main filter caps but I think you have them connected in series, right?
That way it halves the capacitance but adds the voltage rating to 600v.
Look at the schematic for #102. Your balance resistors should go from + to - on each cap with the negative of the second cap going to ground #4.

3) try different snubber caps on V2 starting with 25pf. If it is too bright start going up in value.

How does your presence work? I can't tell by the presence cap which way the polarity is.