RCI 2950, zero VCO voltage

[SmoothRadio912]

Yikes...20MHz - sigh, ok, this does not sound good.

The Main PCB may be more of your problem than the CPU /Display - so you know.

This is similar to the "HR2510" Chip failure - the problem isn't the "chip" it's the PLL03A programming failure - once the main ROM in the (Big) chip is corrupted, it's done - looks pretty but it's motors shot...PLL can't do much when it doesn't know where to go or what to do...

In your case, I hope it's just a Main PCB board failure like the 5V regulator the PLL needs - because of issues around the older TTL and some CMOS devices of yesteryear, if they get power from pins and the device isn't fully powered up - the logic section blows up - acts like reverse polarity power hookups.

Where is this 5v regulator that controls this?

 

[Handy Andy]

You said you checked Regulators - so not sure of (again) your board - but IC4 is your PLL's 5V and it uses caps too so if they are going bad - this can affect PLL...

Again presuming you have a board like that I've shown...


Else older version uses this layout

​

 

[Handy Andy]

In older versions the IC4 setup was a little too close to the edge of the board for many - I found several boards that had power issues from BLOWN traces going to this spot - so look for them - doesn't hurt to swap out for fresh caps here too...

 

[SmoothRadio912]

In older versions the IC4 setup was a little too close to the edge of the board for many - I found several boards that had power issues from BLOWN traces going to this spot - so look for them - doesn't hurt to swap out for fresh caps here too...

Excellent, thank you for your help here. Just trying to gather as much info as I can. And it has the older board, EPT295013z

 

[SmoothRadio912]

Well that regulator is functional, providing 5v to the CPU board.

 

[Handy Andy]

It's providing 5V ?

Hmmm The CPU is supposed to provide it's own...because the "5V" the main PCB provides only powers just part of the CPU board...

Ok, I'll have to look a little harder into my notes about this...

I have a dinner date with my wife and Oscar Meyer
...I do have priorities...​

If voltage is steady Check voltages on CN606 - that is the one that sends data to the PLL on where to go.

It uses a programmable Serial Data PLL - so a clock and stuff (Enable and Data lines too) has to be present for the transfer of data to and from that PLL section.

 

[Handy Andy]

Ok, I'm going to have you check to see if you're getting 8V or even 5V from the CLARIFIER...

IF you don't then there's our answer - not the PLL not the CPU, the Clarifier.

Reason?

You're 20MHz - sounds like the Clarifier may have quit. Odd to happen but not impossible - so look for voltages...

You did claim that you aren't seeing Main PCB 10MHz clock - so look for Clarifier and if that is dead, you have at least found the symptom, you have to track down that loss. Start at J118 (if your board is discrete) - 3 wires by VR21 (it was why we even needed to know if you have 5 volts available) See if you get any voltages out.

Locate the "fine" pot on the front panel and see if any lines have voltage, then try to see if you can locate the wiper - and trace it back to main PCB thru onto a (possible) Disc cap and Resistor R213 (10K) on the Main PCB...but it's in the VCO "block" area that CN606 goes to, there is a line from the Front panel that routes to here...It's supposed to go back thru J118 but if there is an open in the Trace and things seem to work except no voltage - check that VCO card - it needs what J118's got. IT needs to go and power an Xtal...X2 by IC14....