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Re: GReg-Electrical Tech Journal Redux

Posted: Fri Mar 21, 2025 11:26 am
by Greg
Built three Mid Side Matrixes.

Re: GReg-Electrical Tech Journal Redux

Posted: Tue Mar 25, 2025 6:40 pm
by Greg
Finished 42 Direct boxes, built by JSP.

Re: GReg-Electrical Tech Journal Redux

Posted: Thu Mar 27, 2025 8:47 am
by Dr Tony Balls
Greg wrote: Thu Feb 20, 2025 9:05 pm
Image
Atr power supply
Do you mind sharing what model Hakko Desoldering gun that is, and are you satisfied with it?

Re: GReg-Electrical Tech Journal Redux

Posted: Thu Mar 27, 2025 10:03 pm
by Greg
Dr Tony Balls wrote: Do you mind sharing what model Hakko Desoldering gun that is, and are you satisfied with it?
I think it's the FR-301? I'll double check when I'm back there.
It's not as good as the bench PACE station we have, but it does 95% of what you need. I'd recommend it.

Re: GReg-Electrical Tech Journal Redux

Posted: Thu Mar 27, 2025 10:24 pm
by Greg
-Elsewhere-

Studer C37 1/4" 2-track
Intermittent sputtering noise in record mode, left channel.

It was misunderstood as a repro issue, so I started probing and poking the repro amps, trying to stimulate problems. Not getting anywhere, thinking it was a thermal issue, bad contact or broken solder joint, I just reflowed and cleaned the solder joints on the pcb. This noise is similar sounding to one the Ampex 351s would make sometimes, which ended up being the board's aging, heated joints. I found a microphonic tube that would ring at somewhere between 14k and 16kHz when tapped. Almost sounded like a feedback oscillation for a second.
When I did a simple record test, the sputtering noise came through in a clear burst. I could get it to happen once in roughly 4 or 5 times I tried recording.
Tapping around the record amplifier, I found one of the relays would cause the sputtering if nudged. I swapped it out with the other one on the board, cleaning the contacts in the process. There are two relays which are responsible for switching the EQ standard and speed associated calibration pots. This seemed to solve the problem, at least that day. I put it into record, for an entire reel (30 min) recording the outputs into pro tools so I could do other things, and come back to quickly scan for noises. Did a bunch more little tests to try to get it to happen again. All was good. It looks like I canget NOS relays, so I'm going to get a couple.
I recalibrated since a bunch of tubes had been swapped around and other monkey business.

Re: GReg-Electrical Tech Journal Redux

Posted: Fri Mar 28, 2025 12:25 pm
by Nate Dort
Greg wrote: Thu Mar 27, 2025 10:03 pm
Dr Tony Balls wrote: Do you mind sharing what model Hakko Desoldering gun that is, and are you satisfied with it?
I think it's the FR-301? I'll double check when I'm back there.
It's not as good as the bench PACE station we have, but it does 95% of what you need. I'd recommend it.
I had a Hakko 808 desoldering gun for like 15 years before the heating element died and they stopped supporting it. Got an FR-301 (direct from Japan via ebay, it was the best price by far even though it's the 100VAC input version) and it works great.

Re: GReg-Electrical Tech Journal Redux

Posted: Fri Mar 28, 2025 12:32 pm
by Dr Tony Balls
Nate Dort wrote: Fri Mar 28, 2025 12:25 pm
Greg wrote: Thu Mar 27, 2025 10:03 pm
Dr Tony Balls wrote: Do you mind sharing what model Hakko Desoldering gun that is, and are you satisfied with it?
I think it's the FR-301? I'll double check when I'm back there.
It's not as good as the bench PACE station we have, but it does 95% of what you need. I'd recommend it.
I had a Hakko 808 desoldering gun for like 15 years before the heating element died and they stopped supporting it. Got an FR-301 (direct from Japan via ebay, it was the best price by far even though it's the 100VAC input version) and it works great.
Yeah! They have a grey market version on Amazon for like $125 less than the proper version and I think its the same thing. Surprised that the 100V works fine, but maybe I shouldnt be.

Re: GReg-Electrical Tech Journal Redux

Posted: Fri Mar 28, 2025 1:06 pm
by Nate Dort
There are some people who have modded their 100V version to work with 120V, but others have reported that it's not necessary unless you're really concerned about vacuum motor running too fast.


https://www.youtube.com/watch?v=4uwo3d36nWk

Re: GReg-Electrical Tech Journal Redux

Posted: Thu Apr 03, 2025 4:35 pm
by Greg
Finished 2 EAPreqs (2-channel rack) before my session today, so I could test it in action. I like it when I get a chance to do a whole band or set of drums through them. Usually, there aren't enough channels in the room to do that, but studio B has 12 for today, if you include the Normaphones. Unfortunately, it's not a full band setup, but at least it's some good, quiet,critical listening acoustic stuff.

Old Josephson C609 (e22 prototype)-

Noises on the output.

The XLR barrel mounting screws were loose (not a possibility on the production mic). This happens when there's been a lot of rough pluggin/unplugging.

Re: GReg-Electrical Tech Journal Redux

Posted: Wed Apr 30, 2025 12:22 pm
by Greg
Some simple stuff-

Neumann U48-
No output.

Broken wire on the mic cable (carrying one leg of the output). Cut the cable for a fresh end to rewire to the connector.

ATR #4?

Right VU Meter intermittently working while calibrating today.

Exercised the VU/PPM switch, and came back to life.

DI Boxes and EAPreq500s