| Author |
Message |
    
Surgeon General 108
| | Posted on Wednesday, January 08, 2003 - 10:32 pm: | 
|
I need to know if anyone can provide me with a used "balanced modulator board" for my Tram D201 |
Midnight
| | Posted on Saturday, January 18, 2003 - 12:01 pm: |
|
surgeon, contact me i have 2 old trams 201 for parts e-mail me at rjsmith@asde.net might be able to supply or exchange parts. later the midnight |
Crafter
| | Posted on Sunday, January 19, 2003 - 12:37 am: |
|
Theres some tram stuff on e-bay for sale but I think its part of the vox circuit. |
2600
| | Posted on Monday, January 20, 2003 - 3:11 am: |
|
If you replace the balanced modulator board, be sure it's for the same radio. The original "hand-wire" D201 had all the tube sockets mounted on the steel chassis. The round pins on the Balanced Modulator board are larger than on the later versions, and won't interchange. The next 23-channel version had all the tubes BUT the driver and final on two large printed-circuit boards. The Balanced Modulator board for this one uses smaller square pins. This version looks like the one used on the D201A 40-channel radio, but may lack a couple of parts that they added to the 201A.
If you plan to use SSB AT ALL, I recommend replacing all 5 electrolytic capacitors on this board. You need three) 1uF at 50 Volt parts. I know, the board only runs from 14 volts, but the 50-volt rating keeps the leakage current down. You'll need one 33 uF 25 volt (47uF works okay) and one 100uF 25 Volt (220 or 330 works okay here). The high operating temperature inside a D201 pretty well guarantees that one or more of these will have gone bad after this many years. Electrolytic caps just aren't designed to last 25 years. Changing all 5 of them is usually cheaper than the time spent to test even one of them.
If the board you use has any number of hours on it, expect one of the carrier crystals, 6.2535 MHz or 6.2565 MHz to be intermittent, dead, or drifted off frequency. 25 years is a long time for a quartz crystal, too.
If the reason you're looking for a board is a failed carrier crystal, a used board may just have the same problem. Beware of "stuck" trimmer capacitors. If the trimmer cap seizes and won't turn, the solder that connects the screw shaft on the trimmer to the moving part of the capacitor can break loose if you twist it hard enough. A very close look at the top of these two trimmer caps (next to the two crystals) will reveal a broken solder bond between the screw head and the "silvered" part of the trimmer. If you find this, temporarily bridge across the trimmer. If the crystal comes back to life, but off frequency, it may still be good. Old 23-channel solid-state SSB radios were full of this style trimmer cap. A junker of this era may be easier to find than a source for new ones. This size/shape ceramic trimmer cap is obsolete and may be hard to locate for sale as a new part.
73 |
|
