Hmmm...
I'm not sure it's the bridges.
Try hooking it up with one bridge for the entire PSU as such -
The secondary centertap will be made by connecting the 'middle' of the two secondaries together.
I'm not sure it's the bridges.
Try hooking it up with one bridge for the entire PSU as such -
The secondary centertap will be made by connecting the 'middle' of the two secondaries together.
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Hi Zen Mod,
Now I'm worried... I did start it with only one bridge connected but very briefly to check for the buzz. Please tell me I didn't just destroy my amps ��.
Now I'm worried... I did start it with only one bridge connected but very briefly to check for the buzz. Please tell me I didn't just destroy my amps ��.
J is one tough bugger ....... but only you can test that
start with measuring DC offset on output - it must be near 0
then check Iq
if that's good , connect test speaker
however - as you said that you are again hearing some buzz , it's likely that amp survived ......
what you did is same as that you cut your own leg , to check will you be still wobbly , after 2 beer packs last night
start with measuring DC offset on output - it must be near 0
then check Iq
if that's good , connect test speaker
however - as you said that you are again hearing some buzz , it's likely that amp survived ......
what you did is same as that you cut your own leg , to check will you be still wobbly , after 2 beer packs last night
Hi JSA,
If you have spare bridge rectifiers you might just switch your current set out.
Otherwise, I would just continue as the Mighty ZM suggested.
Cheers,
Dennis
If you have spare bridge rectifiers you might just switch your current set out.
Otherwise, I would just continue as the Mighty ZM suggested.
Cheers,
Dennis
Hi Zen Mod,
In shear terror I dug up an old pair of in wall speakers destined for the garbage and hooked them up, using my iPod as a source and after a lot of sweating and panicking the music becan to play! Both channels working, music gets quite loud actually. The transformer buzz can be heard through the speakers though when no music is being played or the iPod isn't plugged into the input. Bias is 411mv on both channels, dc offset 0.01 and 0.04. I can hold my hands on the heatsinks for 8-10 seconds when the amp has been running for an hour.
I've also noticed and audible clicking sound when I put my ear close to the transformer, and it comes through the speakers as well.
I'll have to try 6L6's idea later, and report back.
In shear terror I dug up an old pair of in wall speakers destined for the garbage and hooked them up, using my iPod as a source and after a lot of sweating and panicking the music becan to play! Both channels working, music gets quite loud actually. The transformer buzz can be heard through the speakers though when no music is being played or the iPod isn't plugged into the input. Bias is 411mv on both channels, dc offset 0.01 and 0.04. I can hold my hands on the heatsinks for 8-10 seconds when the amp has been running for an hour.
I've also noticed and audible clicking sound when I put my ear close to the transformer, and it comes through the speakers as well.
I'll have to try 6L6's idea later, and report back.
few pictures could help
also - you told nothing about xformer itself - size and origin (at least fast glance upwards didn't reveal that to my old eyes)
also - you told nothing about xformer itself - size and origin (at least fast glance upwards didn't reveal that to my old eyes)
Hi Zen Mod,
The xformer was a custom order from Primrose here in Canada. It's a 400VA toroidal with 120v primary, and dual 18v secondaries. The manufacturer provided the following specs for the transformer:
Secondary:
1. 18v full load, 19v off load, Iac 11.20, output VA 202
2. 18v full load, 19v off load, Iac 11.20, output VA 202
Here are a few pics from different angles and zoomed in on different areas. The chassis is a little cramped, in retrospect I should've gone for the deeper 4U chassis.
The xformer was a custom order from Primrose here in Canada. It's a 400VA toroidal with 120v primary, and dual 18v secondaries. The manufacturer provided the following specs for the transformer:
Secondary:
1. 18v full load, 19v off load, Iac 11.20, output VA 202
2. 18v full load, 19v off load, Iac 11.20, output VA 202
Here are a few pics from different angles and zoomed in on different areas. The chassis is a little cramped, in retrospect I should've gone for the deeper 4U chassis.
Sorry, the pics will come asap. The site is not currently allowing me to upload pics, says there's an error.
You have a black wire connected to the positive (+) out from one of the rectifier bridges.
Ok if connected correctly on the PSU board, but confusing to me.
Ok if connected correctly on the PSU board, but confusing to me.
Hi NicMac,
I started running out of wire colours so for the rectifier outputs I made the (+) black, and the (-) white. So yes, By "standard" colour codes I can see why you would be confused.
I started running out of wire colours so for the rectifier outputs I made the (+) black, and the (-) white. So yes, By "standard" colour codes I can see why you would be confused.
try different bridges
if buzz persist - disconnect one channel completely from PSU
if buzz goes down , issue is load - meaning - Donut is bad for task
also worth thinking of possible DC in mains but that's less likely possible
have you problems with any other amp , connected to wall juice in same place ?
if buzz persist - disconnect one channel completely from PSU
if buzz goes down , issue is load - meaning - Donut is bad for task
also worth thinking of possible DC in mains but that's less likely possible
have you problems with any other amp , connected to wall juice in same place ?
So I hooked up the amp as per 6L6's suggestion and the transformer buzzed regardless of which bridge I used. Zen Mod, I'll try one board at a time to see what happens and report back. As for noise on any other amp, there is no noise at all. I've got a Sansui AU-717 circa 1977 that is dead silent on the transformer and outputs, before and after the full recap last year.
Hi Zen Mod,
I hooked up the xformer with both secondaries on the bridges, then disconnected one channel at a time from the ps board. Regardless of which channel is hooked up on its own, the xformer buzzes.
I hooked up the xformer with both secondaries on the bridges, then disconnected one channel at a time from the ps board. Regardless of which channel is hooked up on its own, the xformer buzzes.
JSA1971 - looks like one of Richards SumR/Primrose transformers. He might have a solution for you if you let him know about the buzzing and the application.
BK
BK