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Hey there Lee - sent you a PM. OEM handles are fine, will match up w/ my other 700b. Thanks!

In all honesty, I'll be on the lookout for some real clean ones. Reason being is I'd like to rack this amp up next to my prior 700b build. One day, just for kicks, I think I'd like to try bi-amping some appropriate speakers, lol. Don't know if any of you maniacs have tried that yet... I suspect...

Hi guys - sorry, fighting a head cold this past week. Thank you Joe, got the replacement parts installed. Also redid basically all my wiring to clean things up nicely. Biased both sides to 365 mV DC after letting it idle for ~30 minutes or so, and hooked up to a PL 2000 pre. Using some HPM-100...

ok - went back in, reattached D52L. Pulled cathode of zener D51L. Left Side 20 V AC +15VL: +16.3 V DC -15VL: -16.4 V DC Right Side 20 V AC +15VR: +11.7 V DC -15VR: -11.8 V DC Dialed up Variac to 40V AC Heard a small pop... wisp of smoke coming from VR51L. Powered down. Fuses still intact.

LOL, my bad. Will go back out there. Sorry Joe - over-caffeinated today...

OK, went back in. D52L pulled one leg; opamp remained out of socket. Dim bulb + variac. Grabbed the right side as well for reference. LEFT SIDE 20 V AC +15VL: +9.7 V DC -15VL: 0.0 V DC 40 V AC +15VL: +15.1 V DC -15VL: 0.0 V DC 60 V AC +15VL: +20.2 V DC -15VL: 0.0 V DC 80 V AC +15VL...

I'm on it; see my edited post above as well for reference. I'll wait a few minutes for you to review, then go pull that leg again.

I did indeed (noted at the top ;-))... Just went back, D52L still in circuit. Seeing the 0.6 V DC voltage drop anode to cathode, 1.6 V DC cathode to anode (no AC voltage applied) to amp.

Afternoon Joe - Hope I grabbed these correctly for you... DMM neg lead to (left) control ground test point, DMM ps lead to +15VL and -15VL test points respectively. Also, D52L reconnected, OPA134 removed from socket, dim bulb + variac results. LEFT 20 V AC +15VL: +6.0 V DC -15VL: -4.9 V DC...

Hi George - Yep, actually found the small covered port to do just that. However, Amazon was kind enough to get the newer Hakko out to me, it's already on the bench and in use. I'll probably calibrate the old one and keep it as a backup at this point. Thanks though!

Thanks Joe. Next steps to proceed?

New numbers w/ 100W bulb: At 20 V AC: L: +8.3 V DC R: +0.0 V DC At 40 V AC: L: +0.25 V DC R: 0.00 V DC At 60 V AC: L: +0.25 V DC R: 0.0 V DC Kept going for a bit more... bulb got brighter, etc At 80 V AC: L: +0.26 V DC R: 0.0 V DC At 100 V AC: L: +0.26 V DC R: 0.0 V DC At the same time...

Was supposed to be 100W, but just checked. Had a 72 watt one in there instead. That's now clearly labeled w/ a sharpie. I can rerun any of those measurements in the AM with a 100w or 150w bulb if that's helpful.

Here we go (pulled leg of D52L) At 20 V AC: L: +6.5 V DC R: +0.65 V DC At 40 V AC: L: +8.22 V DC R: 0.00 V DC At 60 V AC: L: +2.0 V DC R: 0.0 V DC Kept going for a bit more... bulb got brighter, etc At 80 V AC: L: +0.25 V DC R: 0.0 V DC At 100 V AC: L: +0.25 V DC R: 0.0 V DC At the same...

Hi Joe - Yes, all voltages were positive, sorry. All rail fuses installed.

On thce DC protect board, measured across Pin1 (L+) and Pin2 (ground) for the left channel; measured across Pin3 (R+) and Pin4 (ground) for the left channel. Also tested Pin6 ground on the left backplane to Pin1 of the DC protect board, and then Pin6 on right backplane to Pin 3 of the DC protect...

Ah, good catch. The relays click ~80 V AC w/ the variac (and no control board), so the fuse will blow by then. Let me remeasure right after dinner. Thanks Joe :-)

Hi Joe - Here's what I see... let me know if my understanding/process is correct for output offset: Bias trimmers set full CCW. Nothing connected at inputs or speaker jacks. Using Variac w/ dim bulb. Bottom row of transistors, star ground connected, control board in place. DMM - Positive lead...

Morning Joe - Results of the above testing. Black lead of DMM clipped to left ground on control board, dim bulb + variac. Brought up slow, 3 stops at 20V, 40V & 60 V AC. LEFT 20V AC -15VL: -4.2V DC +15VL: +4.4 V DC 40V AC (dim bulb starting to light) -15VL: -4.7V DC +15VL: +5.0 V DC...

Update for the day/night. Pulled everything, control board, backplanes, the works. Re-addressed every wire ensuring proper solder flow to both sides of the boards, trimmed up any wires. Put it all back together. Appreciate all the pointers. Ordered the new solder station too, lol. Put it all...