D201 xmit on VFO mod that cut cables on pins 1&3 of S4?

[capn357]

Is anyone familiar with an Xmit on VFO mod for the D201 that involved removing all connections to pins 1 & 3 of selector S4 (crystal/manual selector)?  If so, I could really use a description of that complete modification so that I can figure out what the heck is going on with my handwired D201, which has such a mod.

I'm trying to track down a problem with my manual receive and finding that I can't rely upon the standard troubleshooting and/or schematic because of this mod.

[KneeBiter]

Sounds crazy but have you checked the relay?

[capn357]

Feb 25, 2017 22:25:42 GMT -5 KneeBiter said:

Sounds crazy but have you checked the relay?

No I haven't checked the relay.  I was originally thinking that since the unit works in both receive and transmit in crystal mode that that would indicate that the relay is working, but I guess that only proves that some of the "channels" of the relay work, yes?

Actually, not only is the manual receive dead, but the unit also doesn't transmit (according to bird wattmeter) when the manual/crystal selector is in the manual position.

[2600]

I would start at pin 6 of V302. You should have about 400 Volts DC when the manual oscillator is off, and around 110 Volts DC when the VFO is activated. Two 22k 2 Watt resistors R319 and R320 are in series to drop 400 Volts down to 110 when the VFO is running. If you can't get 100 Volts or so, one of these two resistors may have failed. Mileage is a factor. We replace those two resistors without testing them first as part of a routine 100,000-mile tuneup. The carbon-composition, or "chocolate fudge" resistors are not terribly reliable.

If what you see is 400 Volts ALL the time, in XTL and MAN mode both, this suggests that the VFO is not being activated. This is done by completing the circuit to ground from L302, by the yellow wire on pin 11 of S4. S4 closes from pin 11 to pin 10 only in MAN mode. The orange wire on pin 10 would normally go to pin 8 of the relay, which allows the VFO to activate only for receive.

The dirt-simplest mod to transmit with the VFO is to ground the orange wire from S4 pin 10, and to break the red/white wire at pin 12 of the SYN board's connector. A two-pole toggle switch is all that's needed for this one.

Breaking the wire to SYN board pin 12 shuts down the 4 MHz crystals. The VFO output takes the place of those four crystals. Grounding the orange wire on S4 pin 10 activates the VFO all the time that MAN is selected, both for receive and transmit.

The dirt-simplest mod to the orange and red/white wires has some drawbacks, but it's the most-popular mod for this version of the D201.

There are more-complicated methods, meant to improve the lineup between your transmit and your receive frequency. If other wires have been disturbed, one of those mods may have been used.

We are assuming, of course, that V302 is in good shape and not the cause of the problem.

Maybe.

Oh, and this schematic is correct for the "hand-wired" radio with the VOX feature. www.cbtricks.com/radios/tram/d201/graphics/tram_d201_sch.pdf

73

[capn357]

Feb 27, 2017 0:34:41 GMT -5 2600 said:

I would start at pin 6 of V302. You should have about 400 Volts DC when the manual oscillator is off, and around 110 Volts DC when the VFO is activated. Two 22k 2 Watt resistors R319 and R320 are in series to drop 400 Volts down to 110 when the VFO is running. If you can't get 100 Volts or so, one of these two resistors may have failed. Mileage is a factor. We replace those two resistors without testing them first as part of a routine 100,000-mile tuneup. The carbon-composition, or "chocolate fudge" resistors are not terribly reliable.

If what you see is 400 Volts ALL the time, in XTL and MAN mode both, this suggests that the VFO is not being activated. This is done by completing the circuit to ground from L302, by the yellow wire on pin 11 of S4. S4 closes from pin 11 to pin 10 only in MAN mode. The orange wire on pin 10 would normally go to pin 8 of the relay, which allows the VFO to activate only for receive.

The dirt-simplest mod to transmit with the VFO is to ground the orange wire from S4 pin 10, and to break the red/white wire at pin 12 of the SYN board's connector. A two-pole toggle switch is all that's needed for this one.

Breaking the wire to SYN board pin 12 shuts down the 4 MHz crystals. The VFO output takes the place of those four crystals. Grounding the orange wire on S4 pin 10 activates the VFO all the time that MAN is selected, both for receive and transmit.

The dirt-simplest mod to the orange and red/white wires has some drawbacks, but it's the most-popular mod for this version of the D201.

There are more-complicated methods, meant to improve the lineup between your transmit and your receive frequency. If other wires have been disturbed, one of those mods may have been used.

We are assuming, of course, that V302 is in good shape and not the cause of the problem.

Maybe.

Oh, and this schematic is correct for the "hand-wired" radio with the VOX feature. www.cbtricks.com/radios/tram/d201/graphics/tram_d201_sch.pdf

73

Thanks a lot for taking the time to detail this process; I had hit a bit of a wall with my own attempts to troubleshoot this.  I'm going to give this a shot first thing when I get back home from taveling.

[capn357]

Feb 27, 2017 0:34:41 GMT -5 2600 said:

I would start at pin 6 of V302. You should have about 400 Volts DC when the manual oscillator is off, and around 110 Volts DC when the VFO is activated. Two 22k 2 Watt resistors R319 and R320 are in series to drop 400 Volts down to 110 when the VFO is running. If you can't get 100 Volts or so, one of these two resistors may have failed. Mileage is a factor. We replace those two resistors without testing them first as part of a routine 100,000-mile tuneup. The carbon-composition, or "chocolate fudge" resistors are not terribly reliable.

If what you see is 400 Volts ALL the time, in XTL and MAN mode both, this suggests that the VFO is not being activated. This is done by completing the circuit to ground from L302, by the yellow wire on pin 11 of S4. S4 closes from pin 11 to pin 10 only in MAN mode. The orange wire on pin 10 would normally go to pin 8 of the relay, which allows the VFO to activate only for receive.

The dirt-simplest mod to transmit with the VFO is to ground the orange wire from S4 pin 10, and to break the red/white wire at pin 12 of the SYN board's connector. A two-pole toggle switch is all that's needed for this one.

Breaking the wire to SYN board pin 12 shuts down the 4 MHz crystals. The VFO output takes the place of those four crystals. Grounding the orange wire on S4 pin 10 activates the VFO all the time that MAN is selected, both for receive and transmit.

The dirt-simplest mod to the orange and red/white wires has some drawbacks, but it's the most-popular mod for this version of the D201.

There are more-complicated methods, meant to improve the lineup between your transmit and your receive frequency. If other wires have been disturbed, one of those mods may have been used.

We are assuming, of course, that V302 is in good shape and not the cause of the problem.

Maybe.

Oh, and this schematic is correct for the "hand-wired" radio with the VOX feature. www.cbtricks.com/radios/tram/d201/graphics/tram_d201_sch.pdf

73

I finally got the opportunity to try out this procedure.  In Xstal mode I measure approximately 430 volts on pin 6 and in manual mode that drops to approximately 68 volts, so "something" is happening there at least.  Both are measured with a very cheesy craftsman multimeter that certainly leaves much to be desired.  Speaking of that cheesy meter, it measures R319 and R320 (in circuit) at approximately 26K ohms each as opposed to the rated 22K ohms.

[capn357]

Still no joy figuring out what I did to break the manual receive on this unit, but thinking back to what I may have "hit" during my cleaning of the unit, I started looking at the large red coil (L301 I believe) connected to the manual tune capacitor.  I don't see anything wrong there (i.e. the two wires seem to still be connected), but I can get the manual receive to at least make a popping noise if I tap on the top of that coil.  Is there more to that coil than meets the eye or is it as dirt simple as it appears?  Anyone ever seen that fail?