Recent content by Mud Duck 486

Noticed this is an old post, but just wondering if you still had any of those switches available?

Well some quick good news! I was able to get the 1-648 finally TX-ing, so I can concentrate my efforts directly on the 1-678. So after reviewing your sams with red lines drawn, my unit is not the same... it looks like there is 8.78v on pin 22 and zero on TX. I am reading 9.37v and 55mV when...

Will do.. I'll let you know what I find. Thanks!

Also a correction, I have the 648 not a 641.. was hoping a switch of the PLL's, to at least see if RX came alive on 678 was my plan but once inside realized they are diff because of the delta tune the 678 has so that put a stop to that thought!

So luckily I have the radio out right now and just tested PIN 22 for 9V. It started with 9.12volts and then slowly is draining off and just continues to.. I had noticed this previously and was wondering if the 9v regulator circuit is compromised.. Who controls the 6 & 9 volts in these radios?

Thanks for the info! Yeah, I've never dived into fixing a radio with PLL problems before so still learning about gains and how they affect the crystals.. I had tested the gains of my transistors and found some where well below their HFE manufactured range which is why replacement was occuring. I...

Hello gentleman, I too have a 641 and a 678 that have PLL issues. The 641 will RX but not TX and the 678 does not RX or TX.. I replaced all the C460 transistors and C710s..plus tried new chips in both and to no avail.. The 641 has all the correct Freq. outputs displaying per synth alignment so...