Re: conrad-johnson pv5
- From: Peter Wieck <pfjw@xxxxxxx>
- Date: Sat, 28 Jun 2008 13:30:41 -0700 (PDT)
On Jun 28, 2:18 pm, eri...@xxxxxxxxxxx wrote:
On Jun 27, 3:00 pm, eri...@xxxxxxxxxxx wrote:
On Jun 25, 3:25 am, Patrick Turner <i...@xxxxxxxxxxxxxxxxxx> wrote:
eri...@xxxxxxxxxxx wrote:
Hi!
For the next few posts a necessary, I will be asking some
questions about the innards of the cj pv5 preamp. So I would
appreciate help from anyone familiar with the unit.
There is a bank of 4 blue 2.2 uf 400v caps in the power supply that
supply plate voltage to the tubes. Are these caps polarized? I
replaced them with auricaps of the same value which are non-polarized.
I powered up the unit, the normal delay occured, the output stage
clicked in and about 10 seconds later I was rewarded with a loud boom.
Now there is no output from the preamp.
Thanx.
ESTG/
Hehe, The God Of Triodes doesn't like ppl who
fiddle around with tube gear without having a deep understanding of what
thay are doing.
He sure doesn't like ppl fitting fancy-shmancy audiophile whatsit do-das
that may make the sound worse, although ppl on the Net have said
the replacements will improve the sound.
Maybe a cap you put in exploded because it shorted internally
from the applied Vdc being higher than the 400V rated Auricaps.
Or an Auricap was faulty.
Or you made a wiring mistake,
Or a splash of solder fell over two places in the circuit
and caused something to heat up.
Non polarized polypropylene caps like Auricaps
can be used where electrolytic polarised caps may now be used.
But the dc voltage rating must be high enough.
Guys doing such replacements of caps should understand the schematic,
and if they cannot
get a copy, be prepared to read the existing circuit and be able to
draw up the full schematic by looking at the unit and armed with pencil
and paper.
They'll measure all the Vac and Vdc voltages, and know why they exist..
Then if they replace caps, they will be competent to work out
what values and types of caps are best and in what position.
Unfortunately, its technical work far beyond the capabilities
of many diyers or audiophiles.
I am a working tech, and sometimes have to repair amps after a
succession of
ppl have modified something but without any understanding.
Patrick Turner.- Hide quoted text -
- Show quoted text -
Hi to all respondents.
I am finally back on the air after my internet dsl connection took a
vacation for 5 days. Problem now appears solved.
Thanx for your responses so far. I will try to address all the
comments/suggestions etc in further posts.
This is my second attempt to get these threads going. About an hour
ago I was smack in the midst of a ten minute effort when the power
company said "thats enough" and the power went bye bye.
Please be patient with me and look for further posts later tonight or
tomorrow.
ESTG/
"The time has come, the walrus said
to talk of many things;
Of shoes- and ships- and sealing-wax- of cabbages- and kings-,
And why the sea is boiling hot- and whether pigs have wings".
.....Lewis Carroll
"Through the Looking Glass"- Hide quoted text -
- Show quoted text -
Ok Here goes:
Peter W.:
The auricaps are NP - nothing in their description says
otherwise. However, one lead is black and the other is red, and I read
somewhere {not in the Parts Express description) that the black lead
should be connected to the incoming signal and the red to the outgoing
signal. I took this to be some audiofile stipulation not an electrical
requirement.
In any case, I have replaced the originals to see if that solves the
problem. It does not.
The boom came through the speakers.
There are no visible signs of damage inside the unit (no burnt parts
or scorching on the circuit board).
Soldering technique first rate -no solder splashes, bridges, cold
solder joints etc.
I was motivated to replace all the caps because the unit is 23 years
old. I did so in stages, this being the 3rd stage: 1st- update to the
power supply recomended by CJ. 2nd- Changed all caps in the output
sections- used auricaps where CJ no longer stocked parts. Result so
far a very noticeable increase in clartiy/resolution. SO, I got
greedy! decided to change the caps in the power supply that fed base
voltage to the tube plates. Thats where trougle began.
ESTG/- Hide quoted text -
- Show quoted text -
Do you have the means to test the caps (both the ones you put in and
the ones you took out)?
If one of them failed, then something downline also failed, hence the
*BOOM* and the fact that the simple replacement didn't take.
Do you have the means to test the tubes? One of those could have
shorted - and be entirely unrelated to the caps.
Do you have the means to measure the current draw on the unit? Not
that this will tell a great deal, but if it is excessive, it could be
indicative of whether the problem is in the power-supply or beyond. If
both channels are silent, that would kinda-sorta indicate the power-
supply. So, do you have the means to test the various voltage points?
Without the schematic *and* the unit in front of me, and a couple of
tests, I am entirely shooting in the dark and shooting generic
questions into that darkness to boot.
Peter Wieck
Melrose Park, PA
.
- References:
- conrad-johnson pv5
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- Re: conrad-johnson pv5
- From: Patrick Turner
- Re: conrad-johnson pv5
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