Help identifying germanium TO-3

[Delta362]

I have a 1967 RMI-140 in for repair. The two output germanium transistors are bad. I don't have the schematic yet to know the circuit parameters. I am unable to find any information on what these may have been.

Markings are 466, 7292955, 6717. I understand the week 17 of 1967, but can't seem to cross their own part number markings with any manufacturer's version. Anyone familiar with these or able to perhaps provide some guidance?

[mozz]

NTE 121 if that helps. 466 eia code is Delco, which I have seen marked on transistors before.

[Delta362]

NTE 121 if that helps. 466 eia code is Delco, which I have seen marked on transistors before.

Thank you! I didn't realize the 466 was with EIA code. I should have known better! Thank you for the clarification and current offering!

[Jazz P Bass]

Music Parts has the schematic.
$20.
https://www.musicparts.com/products1...ml?Company=RMI

[Delta362]

Music Parts has the schematic.
$20.
https://www.musicparts.com/products1...ml?Company=RMI

Thanks, Jazz!

[Axtman]

How do you know it is a Germanium transistor?

If I had to guess, I would say it is a 2N2955 Silicon PNP transistor. The other markings, "795," are part of an in-house order number.

[mozz]

The number pops up in the NTE cross reference. Plus, it is 1967 so you on the edge of switchover. I am showing a TO-3 and a TO-18 and a TO-5 package, so 3 totally different transistors there. Also, the TO3 is showing a date code of 1998 so i don't think they made those for 30 years.

[Axtman]

Mozz, You are correct that NTE says NTE121 is the substitute. I recommend Delta362 remove them and test them anyway.

nte121.pdf

[mozz]

I think hopefully he has done that, and that is how he determined they were bad.

[The Dude]

I'm not saying it's the case here, but I've often seen people replace germanium transistors thinking they are bad simply because of the lower voltage drop.

[Axtman]

Or replaced Germanium transistors because of the leakage.

[J M Fahey]

Just thinking aloud.



How were transistors determined to be bad?

What measurements were made?

Values found?

Were they measured in/out of circuit?

Does the amp use a driver transformer?

Is amp single or split supply?

Rail voltage values?

Please add a picture or two, one showing the power amp board, another a full chassis shot.

[Delta362]

I had measured them out of the circuit and the resistance was less than 5 ohms, though I don't recall which terminals gave me that reading at the moment.

The amp had several other issues with it, including numerous caps that physically leaked fluid, a frayed 2-prong power cable, and a damaged speaker cable. Customer elected not to repair so I no longer have the unit.

[Axtman]

Delta362, There are a bunch of really cheap transistor checkers that with the simple press of a button tell you all you need to know about the transistor.

[Delta362]

Delta362, There are a bunch of really cheap transistor checkers that with the simple press of a button tell you all you need to know about the transistor.

Thanks! I have a few of them that I use.