My take on a 2nd Gen ODS

[Raoul Duke]

Good luck! I hope it’s quick and painless!

[ViperDoc]

Thanks!
Been trying to pass a 3mm kidney stone for the past three weeks now. Tomorrow morning I'm having shockwave lithotripsy done to try to smash up the 7mm stone that's still up in my left kidney. I've been dealing with stones for about four years now. I've changed my diet but they run in the family so I'm sort of stuck with them. 0/10 would not recommend!
Matt J.

Brutal. Good luck. Drinking 100% cranberry juice (no sugar added, no BS cocktail--the real deal) helped me dissolve and pass one 20 years ago. Saw that f7cker at the bottom of the toilet.

[Matt J]

Thank you very much for the well wishes!
Cranberry juice (non-sugar) certainly helps! I like adding a little lemon to my water to help break them up some too.

Managed to start wiring up some of the shielded cable today. RG188A from Pasternack. I hate trying to solder to the back of Alpha pots, so I run a separate wire from the shield to the ground bus wire with a heat shrink cover.
Heat shrink colors are different so I can follow the signal flow easier and not miss wire the ends.

Matt J.

[Matt J]

Thanks!
Been trying to pass a 3mm kidney stone for the past three weeks now. Tomorrow morning I'm having shockwave lithotripsy done to try to smash up the 7mm stone that's still up in my left kidney. I've been dealing with stones for about four years now. I've changed my diet but they run in the family so I'm sort of stuck with them. 0/10 would not recommend!
Matt J.

Brutal. Good luck. Drinking 100% cranberry juice (no sugar added, no BS cocktail--the real deal) helped me dissolve and pass one 20 years ago. Saw that f7cker at the bottom of the toilet.

One I passed at work right before Covid hit looked like it was giving me the middle finger, which was fitting considering how it felt.

[ViperDoc]

One I passed at work right before Covid hit looked like it was giving me the middle finger, which was fitting considering how it felt.

Cheesus on a cracker.

I'm not hitting the like button out of respect.

[Matt J]

One I passed at work right before Covid hit looked like it was giving me the middle finger, which was fitting considering how it felt.

Cheesus on a cracker.

I'm not hitting the like button out of respect.

Yeah, there needs to be an "ouch!" button instead!

Last Friday's procedure didn't go quite as planned. Instead of the shock wave lithotripsy they had a to do full ureteroscopy and go up in me to blast both 7mm and 3mm stones out. They were afraid the 3mm stone was causing a blockage and could lead to hydronephrosis. Not fun stuff. They left behind an ureter stent I will have to have for a while to help stuff clear up. I've been in a lot of pain over the weekend and taking things gingerly.

Now back to happier things like amp talk!
I'm not in a physical state to move a full chassis around so I've been cleaning up a few things on the circuit board. It's a mix of Dralorics from Welagen and some NOS Pihers I had. I did add a PI Balance pot to adjust later. One thing I would like some feedback on is the PI circuit. Being that this will be a 50 watt version I plan on running the NFB from the 8 ohm OT tap to a 4.7k NFB resistor. Since I'm using a 12AT7 for the phase inverter with an adjustable presence pot should I leave the PI cathode at 470r as on the original 2nd Gen circuits or switch to a 820r PI cathode seen later amps with a full presence control and 12AX7 PI tube? I have an 820r in there now for the time being.
Matt J.

[martin manning]

...should I leave the PI cathode at 470r as on the original 2nd Gen circuits or switch to a 820r PI cathode seen later amps with a full presence control and 12AX7 PI tube?

I'd say for 12AT7 keep the 470R bias resistor.

[Matt J]

...should I leave the PI cathode at 470r as on the original 2nd Gen circuits or switch to a 820r PI cathode seen later amps with a full presence control and 12AX7 PI tube?

I'd say for 12AT7 keep the 470R bias resistor.

Thank you, Martin!

I did try your OT phase test this evening and came across something odd I would like your feedback on.

I tack soldered in the OT primaries with the CT grounded. Running a 7vac power supply at 120vac wall voltage gave me ~3.9vac on the OT secondaries' 8 ohm tap at the speaker jack. Measuring the blue and brown primaries only gave me ~42.9vac on the blue primary and ~43.1vac on the brown primary. I was expecting a much larger voltage difference of at least ~8 volts between the two. Do you see anything incorrect with how I tested or measured this?

Matt J.

[martin manning]

I'm not sure what to make of that. Are you sure you have it connected correctly?

[Matt J]

I'm not sure what to make of that. Are you sure you have it connected correctly?

I keep thinking I have something miss-wired somehow and I just haven't caught it, or I'm implementing something in the test incorrectly.

I made an 8 ohm load box a while back and added jacks to run to a low voltage power supply so I can provide low AC over a load to the OT secondary. I took a 7volt power supply and modded it with some DMM leads so I can plug it in via the jacks to the 8 ohm resistor, then run a speaker cable like normal from the load box to the main speaker jack.

I took out the Mojotone OT I originally had in and installed a Mercury Magnetics one I was also thinking of using to see if there would be a difference. OT secondaries are wired up like normal to the impedance switch with the black common wire running to the output jack's ground.

OT CT (red wire) is soldered to ground while the blue and brown primaries are tack soldered in to the output tube sockets. I ran the test again and still came out with results like those from the Mojotone OT: ~4 VAC on the secondary, ~44 VAC on the brown and blue primaries.

Matt J.

[martin manning]

Hook-up seems ok, are you measuring the voltages from the plate leads to the secondary hot?

[Matt J]

Hook-up seems ok, are you measuring the voltages from the plate leads to the secondary hot?

Ah, that was the issue! I was measuring the plate voltages to ground instead.

Things were much clearer this time: Blue primary measured 42VAC, Brown primary 50VAC.

Thank you very much again, Martin!

Matt J.

[martin manning]

OT CT (red wire) is soldered to ground while the blue and brown primaries are tack soldered in to the output tube sockets. I ran the test again and still came out with results like those from the Mojotone OT: ~4 VAC on the secondary, ~44 VAC on the brown and blue primaries.

Things were much clearer this time: Blue primary measured 42VAC, Brown primary 50VAC.

Yep, difference is 2x voltage applied at the secondary as expected :^)

[Matt J]

OT CT (red wire) is soldered to ground while the blue and brown primaries are tack soldered in to the output tube sockets. I ran the test again and still came out with results like those from the Mojotone OT: ~4 VAC on the secondary, ~44 VAC on the brown and blue primaries.

Things were much clearer this time: Blue primary measured 42VAC, Brown primary 50VAC.

Yep, difference is 2x voltage applied at the secondary as expected :^)

It's always the little things right in front of you that you fail to see! Reminds me of the saying you hear a lot in my parts "If it were a snake, it would have jumped out and bit me!"

Matt J

[Matt J]

Wired up the power supply today to do a preliminary smoke check before proceeding any further.
Played around with different ways to route the high B+ wires to keep them away from the AC carrying signal wires that will be coming from the phase inverter.
Powered it up slowly with my variac and current limiter.
No smoke, pops, or blown fuses.
B+ values were around what I would expect for an unloaded amp running through a current limiter.

The circuit board is done, but I have more double checking to do before starting to install it.

Matt J.