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Post by bountyhunter on Jan 12, 2024 15:17:57 GMT -5
I recently acquired my first Tram. Nice clean radio. The resistors were already replaced. The radio has a modification I'm not familiar with. Under the bal mod board is a small perfboard mounted. It has an op amp and a few supporting components. 2 of the wires go to V401 Pins 4,8. I'll try to get a pic uploaded. Any help in identifying the mod is greatly appreciated. Thank you.  |
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Post by 2600 on Jan 13, 2024 1:27:38 GMT -5
Well that's a new one. A pic or three would help, especially if the focus is good. Pin 4 on that tube should be where 6.3 Volts AC is being "borrowed" to rectify and filter the DC that runs this chip. Pin 8 is one side of the zero-adjust circuit for the radio's S-meter. Sounds like maybe this was a circuit to adapt an external S-meter?
Haven't see it before.
73
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Post by bountyhunter on Jan 13, 2024 16:49:21 GMT -5
Thanks for the reply. That makes sense because one of the wires goes to the SWR/CAL PWR switch. There's a VR on the perfboard. I'm having trouble getting a pic to upload so here's a link test. photos.app.goo.gl/LpJDMm1QYDMfNwP9AAlso, the VOX is disabled. Is it worth the time to make it functional again? I have another radio that has VOX and it does come in handy sometimes. |
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Post by bountyhunter on Jan 28, 2024 11:30:34 GMT -5
Update: The unknown modification turns out to be the meter zero. Apparently someone didn't like needing matched 6GH8A's.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Jan 28, 2024 13:37:57 GMT -5
Update: The unknown modification turns out to be the meter zero. Apparently someone didn't like needing matched 6GH8A's. It may be the same circuit upgrade that they incorporated in the D201A. Eliminated the matched tube issue. |
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Post by 2600 on Jan 29, 2024 0:43:41 GMT -5
Update: The unknown modification turns out to be the meter zero. Apparently someone didn't like needing matched 6GH8A's. It may be the same circuit upgrade that they incorporated in the D201A. Eliminated the matched tube issue. Cool! Hadn't seen that done, but it's the same meter chip used in the D201A. Definitely an upgrade. 73 |
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