I did not follow this. thread in full but since I¡¯m being at revising some PR40s at the moment, I found that one cause for noisy or weak reverb can be the transistor 2N306?
in the receiver circuit of the spring reverb (AO-33-1). The 100uF emitter capacitor often is anoter culprit.
I dropped in some standard silicon NPN transistor with an hfe (current gain) of 100-300 and it made reverb come back.?
BTW, it is totally normal that the Ohm values of the primary windings differ. Important is the winding ratio. And this is a constant.
The difference in the ?ohmage¡° is that the windings are stacked one upon the other with the circumference changing resultig in different wire lenghts for either winding.
So changing the OT is a shot in the dark.
¡ª
Christoph
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Or maybe a better soldering iron?
On 3/2/2020 9:18 PM, john
alluneedtoknow via Groups.Io wrote:
I was born on Friday the 13th. The amp cleaned up and quieted down
nicely with the new caps and the bass was more full and round, but
it was still noisy with reverb on so I probed further. I ended up
replacing some plate load resistors and did much head scratching.
I isolated the reverb transformer and its secondaries, then
measured each to the center tap, brown/209 ohms and blue/279 ohms,
so I swapped in a better unit measuring 229/245 ohms. These two
actions cured the issue. I played it for 5 days with no
problems,until tonite when I reinstalled it,sounded wonderful,
then POP......! Reverb now MIA,except for some noise,and the
return works when touching the springs, but with reverb off still
good,nice and quiet. Should I give up or purchase a large hammer?
On Sat, Feb 22, 2020 at 12:09, j f
Thank you Scott,
The kit
arrived and I will perform the surgery later today, and
report back.
Regards,
?John
On Mon, Feb 17, 2020 at 0:30, Scott Hawthorn
Replace the caps with the kit from Tonewheel
General Hospital.
On
2/16/2020 9:20 PM, john alluneedtoknow via
Groups.Io wrote:
Gentlemen,
I am hoping someone can shed some light on my
issues, the primary one being distortion and some
"frying egg" noise. The distortion is more
pronounced on lower notes especially with multiple
notes played together. This occurs only when reverb
is on. All tubes are fine as tested in another PR 40
and I replaced the RCA cable from necklace to amp.
Two other minor issues, the reverb is switchable
using the chorale/tremolo switch. The console is
outfitted with the Trek II SS1 preamp if I remember
the model correctly, the Trek folks asked me some
questions then said it was a very early model, and
lastly, the bass isn't as strong as on my other PR
40. Tomorrow, with assistance I will try to confirm
both 15"s are working. In summary the unit plays
clean with reverb off but gets ugly when the reverb
is on.
Thank You one and all,
?John
Christoph