Recent content by sstudley

Hopefully a final update. I pulled the protection board one last time and went through each of the transistors, double-checking for the 4th time pinout and functional state. I went ahead and reflowed the solder pads for the wire-wrap posts, checked continuity on anything that looked even the...

Q7 was in backwards, I am really confused as to how... I know, I make mistakes, but as is so often the case, there's a fair bit more... So I flipped it around, no luck, now the relay isn't closing at all. I pulled Q6 (per MTF), still no luck. I pulled Q5 (per MTF) and still no luck. However, I...

thank you zebulon1, good info. There's a fair bit to grok there. WRT my last post. I should be clear that there's 2 issues, one intermittent. The other consistent. The problem with noise/distortion and the pop at startup and shutdown. I’m with you (MTF, et al.) on the protection circuit not...

I'm back to looking at the adapter switching, duplicate and tape. The ground wire on the preamp was, obviously, a red herring. From the Aux input L+R channels, using a typical 1kHz sinewave @ 150mV, volume pot fully open, I'm seeing 50+dB SINAD and THD of .15% give or take .02% up to the input...

Thanks painttoad. I retired my last homemade dim-bulb tester quite a while ago and opt now for a combination Variac and Ensurpa watts meter. Dim-bulbs are certainly a mainstay of any bench and I still have access to my last. I just find that controlling voltage with my hand and knowing voltage...

Well, this really sucks. The smaller cap didn't help, at least not to my ears. I didn't bother trying to get a trace to see if there was a slight improvement. While I was waiting for the new relay to arrive, I did a few test around the protection circuit, trying to capture a trace that might...

I like the idea. I'm waiting on the relay and some slow-blow fuses. I have other jobs to keep me busy, but I will give it a try, prior to installing the new relay. It'll probably be a day or two before I get back to the 1010. Thanks.

Thanks Larry. I have lots of 2690's. I am curious though, if you believe replacing Q7 will help or resolve the relay timing pop issue? I believe I have an understanding as to the role Q7 has in the low side voltage, energizing the relay coil. But I'm not clear exactly how it impacts the speed or...

Well I added the flyback diode as you suggested, double checked my earlier transistor replacement and recap. Everything was fine. I hadn't done anything with Q7 2SC1384, I didn't have a good replacement for it. No improvement. Voltages look good on all posts. I have ordered a replacement relay...

Mostly good news... The Pioneer SX-1010 sounds lovely! After adjusting DC and bias for what is hopefully the last time, a 20Hz-20kHz sweep at @130mV rms into an 8Ω 100 watt dummy load the THD didn't exceed .6% and ultimately hit a peak low of .013%. Not bad, I can live with that and my friend...

I went through all the switches, pots, etc. for a second time, with the exception of the push-button switches. I hadn't hit those the first time through. It didn't change the THD issue, at least not substantially. Of course it didn't hurt. I did however, find what I believe is the primary...

I need to add some details to my last post. If I send a test signal as stated previously, directly in to the power amplifier's, the results are fine. THD in the neighborhood of .01%. If I do the same to the preamp, excluding everything upstream, mostly switching and downstream, power amplifier...

I have located the main culprit for the lack of bias voltage on the right channel. Turns out several of the wires connecting the amplifier board, and the output transistors were, in at least one case, broken whilst two others broke off with an absolute minimal amount of force. Seems that...

I'm still watching this thread, hoping for a break on this issue. I thought I would post some pictures of the work I have done up to this point in the hopes of someone seeing something I have done that might be causing my bias issue. Baring any insight from the AK community, I probably won't...

0.000 vdc idle power 58 watts 51.36 VDC, -51.29 VDC, -51.29 VDC both channels have these replacements. All 3 have been tightly matched for beta. Right (bad) channel only. Q4 KSA940 IS what I had on hand. Original Q4 2SB528 tested fine. This was a shot in the dark. I will order some KSA1220 to...