[fishski13]

finally soldered in the M-caps, but now getting loud ground hum and tube microphonics in both channels. ohmed all the wiring out - measured fine, even the board mount Phoenix screw-connectors to J1. the attenuator measures fine as well with the input jacks. i even ohmed out the interconnects. my Bijou was working fine before inserting the M-caps. in addition to the caps, here's what i also did:

-shortened and re-routed heater wiring.
-sheilded B+ wire with screen grounded via red wire next to star ground since it is running over the heater wiring.
-re-routed grounding wire; the R channel grounds run underneath the L channel board.
-moved star-ground closer the PS board.

my unsheilded signal wiring isn't perfect as i am going to try some Cardas and silver wire as well, but could this also be the problem? ground wires under the boards? btw, my R channel input wire off the attenuator is green, the L channel is red.

i'm glad i waited to tie in a bunch of cable ties to neaten-up/secure the wiring.

what am i missing here?

 

[holland]

Nice, soniccaps everywhere. I have M-caps everywhere, now bypassed with Vit Q for the output.

What if you move the input wiring to the board? Does it change?

On a different note, I noticed you have the voltage multiplier on, cool. I was just thinking about this some of this as I was looking over my PS recently. The loss of voltage seems to primarily come from the CRC filters. One can change the values to lessen the voltage drop across the filter, and get better ripple into the transistors, and give plenty of room for adjustment even if the EZ81 output drops to 305V, allowing more current pull.

C6 - 68uF
C4, C5 - 680uF
R7, R8 - 220ohm

Edit: oops, looks like C6 can be 50uF max. You'll get a bit more ripple with 47uF than with 68uF, but, OK...bummer.

 

[fishski13]

i'll try chop-sticking the wiring tonight. i also have a 2nd attenuator and a 100K pot i can try wiring in to rule out the present ground-shunt attenuator. i've looked over and ohmed my wiring multiple times...

Quote:

Originally Posted by holland /img/forum/go_quote.gif Nice, soniccaps everywhere. I have M-caps everywhere, now bypassed with Vit Q for the output. What if you move the input wiring to the board? Does it change? On a different note, I noticed you have the voltage multiplier on, cool. I was just thinking about this some of this as I was looking over my PS recently. The loss of voltage seems to primarily come from the CRC filters. One can change the values to lessen the voltage drop across the filter, and get better ripple into the transistors, and give plenty of room for adjustment even if the EZ81 output drops to 305V, allowing more current pull. C6 - 68uF C4, C5 - 680uF R7, R8 - 220ohm Edit: oops, looks like C6 can be 50uF max. You'll get a bit more ripple with 47uF than with 68uF, but, OK...bummer.

 

[holland]

cool, i was just wondering about the hum and the wire going over the caps. I'm not sure if it'll make any difference, but you hsould be able to just grab it and move it a bit and see if things change.

I have my m-cap onto the case as well, using sticky tie points (I know, suckage, but I didn't feel like drilling bolt holes...lazy). You can try unhooking the cap and elevating it, to see if it changes on one side (i.e., stuff some packing foam underneath).

I know my suggestions are borderline useless, but I don't really know what the problem may be.

 

[fishski13]

i wiggled the caps, signal and heater wiring with no change in buzz/hum.

when i turn off the amp, the buzz/hum disappears immediately.

i shorted the inputs to ground and the buzz/hum is still there. so the input wiring and attenuator are still suspect.

 

[fishski13]

i forgot i had originally done Amphead's mod, removing R9, R10 and C7, but forgot to wire in heater virtual CT 100R resistors to star-ground for the re-wire. all is well now and sounds great!!!

.

 

[chobint]

Funny, I expected the 220uf caps to be a scale version of the 330's. Instead it appears they are a short, fat version. That is they appear to be of the same diameter, just a bit shorter.

Anyway, looks good. Keep us posted.

 

[chobint]

double post

 

[fishski13]

Quote:

Originally Posted by chobint /img/forum/go_quote.gif Funny, I expected the 220uf caps to be a scale version of the 330's. Instead it appears they are a short, fat version. That is they appear to be of the same diameter, just a bit shorter. Anyway, looks good. Keep us posted.

actually, they're only 150uF.

i've only had about an 1 hr on them, but will get a late night session session in tonight. with the HD650, i've already noticed a not-so-subtle improvement. i haven't tried the K701 yet.

 

[holland]

glad you found the problem, fishski13.

I'm not sure I like the VitQ bypass of the M-Cap too much. It's added a different character. It's too "tubey" with some sparkle. It seems to change the 6N1P into more like the 6DJ8, but with more high end. I'm thinking I might get some FT3l, and replace the VitQ. I think I'll skip the Mundorf Silver/Oil and Silver/Gold. Too expensive!

 

[fishski13]

Quote:

Originally Posted by holland /img/forum/go_quote.gif glad you found the problem, fishski13. I'm not sure I like the VitQ bypass of the M-Cap too much. It's added a different character. It's too "tubey" with some sparkle. It seems to change the 6N1P into more like the 6DJ8, but with more high end. I'm thinking I might get some FT3l, and replace the VitQ. I think I'll skip the Mundorf Silver/Oil and Silver/Gold. Too expensive!

yeah, it only took 4 hrs. of trouble-shooting and discharging caps to realize i'm getting older and so is my memory (i turn 34 today). thanks for taking the time to help me out.

i have no issues dialing in B+ with the cap multiplier and EZ81 - as it should be, but have yet to up the current of the input and phase splitter stages with Regal's mod. if i want to run DC heaters, i'll need a dedicated filament TX. the heaters are dead quiet now though...why bother? i wish i had a scope, just for curiosities sake.

i'm using 0.47uF Sonicap Gen I for bypass: Sonicaps

and here's a comparison vs. Gen II:
Sonicap Gen 2

it's nice to have the Bijou back. thus far, the M-caps are a bit more "grippy" - it handles and hugs the curves a bit better. i'm finishing up touches on my FPE face-plate as a B-Day gift for myself. the Bijou has been a long WIP. i've completed 3 big projects since i've last worked on the Bijou. i have boards and parts for a 2-channel B22 in front of me, but have unfinished business with the Bijou. thanks Alex for designing such a wonderful music maker.

 

[zkool448]

34? fishski you're still a pup

Thought I'd share some progress with my Bijou front plate. The vu meter is not the final unit and will be replaced by this with a blue backlight (courtesy of zare):

 

[fishski13]

zkool,
looks great! i like the blue VU meters

 

[fishski13]

those of you with M-caps: did you notice any significant burn-in?

 

[holland]

I didn't notice significant burn-in, but I had some. I didn't particularly keep track but I think somewhere around 72 hours or so. I leave the amp on 24/7 after builds always to check operating parameters. It was about 3 days for me, but subtle if any. I run 330uF + 150uF. Bass came up a bit. YMMV.