Icom 211E no transmit

[llonen]

I am wondering if anyone can help me with this set, I have this radio on the workbench which presented with no transmit or rather no RF output. a look at the service manual I have for and I was able to trace the problem back to R141 which is a 10 ohm half watt resistor on the collector of Q35, which had gone open in a bad way. I checked around the stages looking for a short to ground and did not find anything amiss. The RF stage and final appear serviceable so I reluctantly replaced the resistor and powered up expecting the resistor to fail again.

To my surprise this brought about the restoration of RF output and returned the radio to full operation, about 8 watts out which I understand is about right for the set. It performed faultlessly for about three weeks then the resistor which I had been monitoring closely for failed in the same way

I have attached the service manual any help would be appreciated

[CapLeaker]

Re: Icom 211E no transmit

Put the radio on a good 13.8V PSU. Key the radio in CW and measure the current draw on the PSU and the RF power output. I think Q35 is in charge for TX9V. That means, if this transistor isn't getting any power (blown resistor 141) the radio will not even key up anything at all (no IF oscillator and IF amp and no biasing in the driver circuit). So something is drawing current and that resistor must get really hot. So the first thing I'd look at is the biasing in the drivers circuit. Hope this helps some... 73!

[llonen]

Re: Icom 211E no transmit

I am finding the is very intermittent, having replaced the resistor again, on an external supply the set draws around 3.5 amps on transmit into a 50ohm load while producing 8 watts. The audio sounds good and the radio gets excellent on air reports when working. Q35 is part of the transmit switching, these sets were known for the rf stages self oscillating but was monitoring the radio output when it last failed.

A thermocouple placed upon the resistor and heat sink for q35 showed nothing unusual, that said when the resistor does fail it does so in rapid time, it is performing well again at the moment.

73’s

[stj]

Re: Icom 211E no transmit

is the 9v really 9v and stable?
if it jumps to 12v the current will increase.

[llonen]

Re: Icom 211E no transmit

It measures around 9 volts and appears stable from both bench psu and internal supply, I suspect that I have located the problem, radio killed by tone board more specifically the switch that enables said tone board which shares that line appears to have a ground short. Mechanically it seems damaged and the switched line to the tone board is at groun.

I am not sure where to go now as to get to replace or remove said switch which is located behind three ancient pcb boards and just as antique soldering looks to be a real rats nest.

I have looked for the while wire leaving the defective switch with a view of terminating it, but don't seem able to find it

[llonen]

Re: Icom 211E no transmit

Well hopefully the problem has been resolved to a satisfactory outcome, since there are almost no Uk repeaters that still use the 1780hz tone burst for access the feature is somewhat redundant. In view that the switches themselves are probably not available and accessing the area would be a nightmare I was able to hook the wire out from behind the switch and cut it there since it disappeared into the mass of wiring. The 10 ohm resistor (second) replacement looks a little scorched but still reads 10 ohms.

Thank you all for your suggestions

73's