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

I have an HR-2510 that receives fine in AM mode, but warbles in SSB mode (it sounds like you're talking underwater). Where is a good place to start looking for the problem? If you need more details let me know. Thanks!

warbling is a sign of freq instability, i have found that the cause is usually a failing vco circuit on the cpu pcb, it will be producing two frequencies similtaneously, switching rapidly between them.

It is a tricky repair, as most of the the parts are surface mount, and troubleshooting it requires a minimum of a 60MHz analogue oscilloscope, as you need to be able to see the waveform each vco is producing, a analogue scope will show both freq at the same time, a digital scope will not be able to resolve it.

unless you have experience working on surface mount gear, and have the scope there will not be much you can do.

Thanks Scott... I'll dig into it this weekend

the first thing I would suggest trying is replacing all of the electrolytic capacitors around the PLL units, there are four thhat are used to smooth out the control voltages to the VCO's, these are a common issue, as they can fail, and cause that problem, after that then it is time to look at the ceramic surface mount capacitors in the faulty VCO circuit, once you ID which one is playing up.

Try cleaning the glue off the 2 regulator ics on the PLL PCB this glue becomes unstable and conductive with age and can cause wobble as it makes contact with PCB vias in the VCO filter circuit. Make sure you remove all the glue from the PCB both around and under the regulators.