sliver Sunn concert bass voltage problems

[thintheherd]

hey there i have a sunn concert bass (silver) and black version, early 70's that is having some problems with the negative voltage rail. when i got the amp it was having some hissiness from the output. it turned out to be two faulty bc107's in the preamp. while i was in there i was taking some measurement just to make sure everything was solid in the supply and i accidentally shorted a negative side of cap to ground on the preamp board,, the positive side on this cap goes to ground. looking at the schematic below it was C128 at the 45 test point. this test point has a wire that goes to the power amp board and connects to test point 29. from there it travels back goes north and hits a 330 ohm resistor R319 and then through CR306 then to ground. first id like to say that R319 is missing from my amp, there is just a jumper in mine. as a result of this mistake i shorted out the diode.

no big deal, i just replaced CR309 with another. also, from point 29 it travels east to two more resistors and a recitifier. i noticed that R320 and R321 in mine are both 1k and NOT 5.6k and 470 ohm respectively like stated on the schematic. i left those alone because they looked stock and went ahead and brought up the power on the variac. now, i am getting -32 volts on point 45 and not -15 which it is technically supposed to have. i never checked this voltage before but being the cap i shorted was only rated at 25vdc i assume this voltage was never supposed to be this high.

now the preamp board is getting this -32 vdc and the fet's (Q101,Q102,Q103)where TEST POINT 45 leads to via 18k resistors are not getting any voltage on the other end of the 18k'S, how could there be -32 vdc on point 45 and on the other side of the 18k's none?. so basically what is happened is, if i run a signal through the input jack, it initially works and then the signal just fades away as if the transistors are completely saturated, but they are actually not receiving any voltage???. I unhooked the jumper from the power amp board to see if the -32 voltage would change and it remains the same. i checked the rectifiers on both sides and they seem to be ok. the power amp in on back works fine. any help would be great. ENZO? haha...thanks!



EDIT: MOVED TO troubleshooting section!!!! sorry!
http://sunn.ampage.org/site/schematics/concertbass.gif

[Enzo]

CR306 is a zener, did you note that? 15v zener. If you replaced it with a plain old diode, then you will get whatever the raw supply might be, apparently 32v. Is that the case?

[thintheherd]

Enzo, you are absolutely correct. i had not noted that! thank you! oh, by the way i have moved this to the troubleshooting section just so you know. i wil report back to that section of the forum with the results. thanks again!

[J M Fahey]

Hi thintheherd.
Tried to read your 3:14 AM post and had to give up, it's formatted into a narrow column, 3 screens high, my head hurts before getting halfway, phrases are chopped at random, ideas get lost.
It's at least as bad as (or worse) than bad punctuation.
Yet Enzo's 04:20 AM answer and your 4:32 AM reply are full screen width, readable text.
What's up with this new software?

Don't tell me it's *MY* rendering, because everything is in the same screen, same OS,same
Browser.
All times are my time zone (-3GMT) , may differ elsewhere but that's irrelevant to this problem.
Just as an example, I'm narrow-formatting this same text to show how annoying it becomes.

Hi thintheherd.
Tried to read your
3:14 AM post and
had to give up, it's
formatted into a
narrow column, 3
screens high, my
head hurts before
getting halfway,
phrases are
chopped at random
, ideas get lost.
It's at least as
bad as (or
worse) than
bad punctuation.
Yet Enzo's 04:20
AM answer and
your 4:32 AM
reply are full
screen width,
readable text.
What's up with
this new software.
Don't tell me it's
*MY* rendering,
because everything
is in the same
screen, same
OS, same Browser.
All times are my
time zone (-3GMT)
, may differ elsewhere
but that's irrelevant
to this problem.
Just as an example,
I'm narrow-
formatting this
same text to
show how annoying
it becomes.

[Enzo]

JM, this narrow thing is happening to any number of posters. I doubt it is a choice. If someone asked me to format my posts to half width like that, I have to say I wouldn't have the slightest idea how to do it. Obviously you just did it, bit a mystery to me it would be. I claim to have no computer skills at all myself, so I am no help determining the cause of all these odd symptoms lately.

[J M Fahey]

Hi enzo, thanks for answering.
I'm not blaming thintheherd AT ALL, I'm pinning it on a software or configuration bug which, please, take my word for it, makes my head hurt.
I'm stating this whenever it appears, so it sometime gets corrected; silence means accepting it as-is.
I'm not blaming the site Administrator either, he's doing an excellent job, I got here not so long ago yet became magnetized by the huge pool of knowledge and good will I found.
In that spirit, I think that pointing major bugs is a service, sort of.
I won't waste time with the minor ones.
Thanks again.
PS: one suggestion: can't the skin be configured as to show the poster's data , avatar and all, on top, then allowing full screen width to the body text, instead of wasting 1/3 of the usable screen width?
I'm SURE it can be done.
If it's not clear from the software instructions or help, it sure can be asked to its developers.
Thanks.
EDIT:Just measured it: it wastes exactly 30%. I'm sure somewhere there is some configuration box where it's ticked (perhaps by default)
Poster data: Top [--] Side column [X]
Column width: 20% [--] 30% [X]
and something like:
Wrap lines to [28] spaces if ****************

[Enzo]

I don't like it when it gets narrow like we are seeing, but I also do not find it comfortable to read when it stretches all the way across my screen. Think about reading a book if the pages were a foot wide and not in columns. Ewg... In other words I am not put off by that waste.


I'd have to say that pointing it out every time is like pushing the elevator button over and over. The elevator already knows you are there after the first push. All we need to do is explain the complaint down in the bottom section, and then tboy will be aware of it.


I am wondering if somehow the size and shape of the posting window when a post is being written is somehow translating to the threads. And I know some of us subscribe through email or some such, possibly that is involved.

[thintheherd]

that zener switch worked by the way enzo. thanks again. amp is operating a full power and sounds amazing!

[Enzo]

Great, glad we found it right off the bat. The ideas come from the evidence.

[J M Fahey]

Ok Enzo, agree.
I thought the elevator button was dirty and pushing it repeatedly would clean it but if you think the message is already reaching wherever it should, that's good enough for me.
Now back to the soldering iron.
Thanks.