The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Hello Everyone.
Just recently picked up one of these units ( 18 ch ssb ) The problem is no rec / tx . Can hear static / PLL is in Unlocked postition ( 861 chip ) getting around 5v at prog pins and around the chip. TX / RX light works ( ie it is switching ). Static is fairly loud ( not dull ) squelch and other buttons work , but again no tx / rx .
Are the diagrams easy to come by as Ive searched around and found zip.
Oh and the easiest thing I have done was changed the chip but no joy.
Any help .....would help.
Thanks from Aus.

I think this is the same radio as the J.C.Penney 981-6203 if so check Q4 and Q6 they go O/C and cause no RX/TX. if you have a diagram send it to me and I will check it out and let you know what to test.

Rick.

Hi ya Rick !

Thank you so much for your response. No I have not found a diagram YET.
Just an update on the radio...I put a "clamping voltage " on the PD output of the 861 and low and behold it started working ( still unlocked at pll )...Im stumped at this tells me the VCO is working but the chip has been replaced.
I will try your suggestion.
Thank you again Rick...regards Ray on Aus !

Is it a case where the VCO is not running, I know you have put a clamping voltage on the PD, but if the VCO will not start a switch on the PLL may just shut down, I know this happens with the 858 PLL and can make it hard to diagnose the fault. If you have a scope, maybe it would be idea to put the scope on the PD pin and see if it has any output at switch on, if not it may well be a bad PLL. It maybe worth replacing the PLL active filter caps. Is pin 24 ground or is it pulled-up to VDD? Pulled-up is the BCD/ROM Mode and pulled-down or ground is 8 bit-binary Mode, this may affect the VCO range. Hope this helps. Lets us know how you get on.

Rick.

Will do Rick. Many thanks...