Sal recommended some additional tests which I completed earlier. I found that the amp is blowing fuses on each power up whenever any rectifier is installed, regardless of which power tubes are (or are not) installed. Also tried an alternate set of 12AU7s with the same result (blown fuse). The two(?) times that the amp powered up without a blown fuse seem to have been flukes. So I can't re-test the voltage on pin 8. There's something else going on. Total guess on my part, but... maybe a bad tube socket?
+3
Bob Latino
kevinmi
skriefal
7 posters
Assistance with ST-120 problem?
skriefal- Posts : 135
Join date : 2011-09-20
Location : Utah, USA
nmchiefsfan- Posts : 78
Join date : 2012-03-21
Quad Cap, perhaps? A section could have gone bad. Have you measured the cap or possibly the chokes?
skriefal- Posts : 135
Join date : 2011-09-20
Location : Utah, USA
I don't know how to measure either of those.
Sal- Posts : 221
Join date : 2009-02-05
Location : Central New Jersey Dynaco-ST70.com
Scott, I sent you a PM, give me a call tonight before 11pm eastern time.
Regards,
Sal
Regards,
Sal
skriefal- Posts : 135
Join date : 2011-09-20
Location : Utah, USA
nmchiefsfan wrote:Quad Cap, perhaps? A section could have gone bad. Have you measured the cap or possibly the chokes?
Your guess is probably correct. Looks like a probable bad/failed section in the quad cap. Replacing the quad cap is beyond my current skills level, so I'll be sending in the amp for repair.
I'm curious to know whether the failed quad cap is a symptom (Weber rectifier failed and took out the quad cap), or whether the failed quad cap is the source of the problem. Or if it's even possible to determine this?
The amp will be singing again soon, so there's something to look forward to!
Thanks Bob and Sal!