[TenTec] Corsair II AGC issues

[Bwana Bob]

Also shoot some contact cleaner into the AGC toggle switch.


					73,

					Bob WB2VUF

Dr. Gerald N. Johnson wrote:
> On Fri, 2008-02-08 at 20:51 -0500, Dave Perrin wrote:
>> Hi-
>>  I have a Ten Tec Corsair II that has some AGC and S meter problems:
>>   AGC toggle switch has no effect at off or slow. At fast it will cycle from no signal to pinned S meter then de-sensed fully and repeat at 5 second intervals with a strong signal. Distorted audio with the same strong signal input.
> 
> Its audio derived AGC, so the time constants have to be a bit longer and
> the capacitors bigger. Check electrolytic capacitors on the IF/AF board
> for being open or having a high power factor. Replace them with low ESR
> types from Mouser.
> 
>>  On the IF/AF board, number 80984- the 10K pot labeled R1 on the board looks like R59 on the schematic. It should adjust the S meter. The pot. is located on the board about half way across and away from the front panel on the bottom of the rig. On the schematic it is located near the left edge and midway up the schematic. The part measures about 8 Volts on all terminals. It also measures the variable resistance that it should. It has no effect  when adjusted fully. 
>>  I wonder if different rigs may have different IF/AF boards with different schematics relative to manufacturing dates. Mine is 02739.
>>
> Could be. I'd believe the single pot near connector 46 is the s-meter
> pot. The other two set CW side pitch and amplitude. There is a 10K fixed
> resistor R1 in my schematic that could be close to the pot R59.
> 
> The meter switch can't be in the IC position to read on receive. So that
> might explain the same voltage on both ends of the s-meter pot.
> 
> AGC is derived by some op amps and detected by D6 through D9. Its turned
> off by Q7 or the front panel switch. Time constants are set by C32 and
> C33.
> 
> Open connections on these insulation displacing connectors used for the
> interconnects are not rare. Nor are opens between the connectors and the
> PC board pins. And many board grounds depend on the board mounting
> screws where the pressure gets relaxed because the plastic PC board
> material lives up to its name and flows under pressure to relieve the
> pressure. Clean the connections with DeoxIT and tighten the board
> mounting screws.
> 
>>  Any ideas or suggestions?
>>
>> 73 de Dave in NH
> 
> 73, Jerry, K0CQ
> 
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
> 
>