CPI 2000 issues

[tramd]

Those two wires soldered to pins 1 and 3 are on U600G. As others have stated, it's one of the programmable dividers. It was done for a 5KC mod to get the "A" channels. Here is the SAMS #168 manual for this radio. It's actually for the 400 mobile, but is very similar to the 2000. It's the only one for the CPI models. It has decent schematics. After looking at the board pics and the parts list TM86 was correct, they are parts C647 and C639, both 5 NPO at 10%.

 

[nomadradio]

If you replace any of the ICs, solder a socket to the board to insert the IC into.

This has been our policy for replacing any DIP-package chips for decades. You can reduce the heat stress to the circuit board foils by clipping the pins on the old chip, up against the 'shoulder' of the pin where it meets the plastic. Melting the solder and pulling each pin 16 or more times is tedious, but now the holes have only solder in them. Much less stress to the foil pad removing solder and nothing else. Got in the habit of inserting the chip into the socket before soldering the socket to the pc board. Sometimes it's less clumsy to do with the socket loose than after it's installed in the radio.

73

 

[Danzik]

This has been our policy for replacing any DIP-package chips for decades. You can reduce the heat stress to the circuit board foils by clipping the pins on the old chip, up against the 'shoulder' of the pin where it meets the plastic. Melting the solder and pulling each pin 16 or more times is tedious, but now the holes have only solder in them. Much less stress to the foil pad removing solder and nothing else. Got in the habit of inserting the chip into the socket before soldering the socket to the pc board. Sometimes it's less clumsy to do with the socket loose than after it's installed in the radio.

73

Yes, think I will be doing this the way you and tram d recommend, I ordered the sockets. I am not positive it is the chip that is bad but there is no change on the outputs of this chip compared to the other one, it did not do the same thing

 

[Danzik]

Looks like a 10 kc mod. Tie the constant +5v on pin 1 to bit 1 input on pin 3.
That chip is the first stage of the programmable divider. So altering that first bit will drive radio up or down 10 kc.

Should have a signal in on pin 2 and signals out on pins 11, 12, 13, 14, and 15. The programmable divider is set by the values on pins 3, 4, 5, and 6.

The chip itself is a 74160 BCD counter. According to the schematic I have you could also substitute a Fairchild 9310 if no 74160 chips are available.

I have noticed the signal in on pin 2 stays at 1.976 v and does not change with the channel selector

 

[TM86]

I have noticed the signal in on pin 2 stays at 1.976 v and does not change with the channel selector

If you have an oscilloscope you should see a waveform on pin 2, not just a DC voltage.

 

[Danzik]

If you have an oscilloscope you should see a waveform on pin 2, not just a DC voltage.

This is what I need to do as I have a like brand new B&K scope in the box that a friend hooked me up with, and I have never used a scope before, but its about time ! I also have a coax tap for it that I have never used also

 

[nomadradio]

A 'scope is just a voltmeter with a dot in place of a meter needle. Positive voltage and the dot moves up. Negative input to the probe/vertical channel and the dot goes down. A time base sweeps the dot from left to right at a chosen speed. With any luck your 'scope is new enough to have triggered sweep. Lets you hold a waveform steady on the screen, starting the left-to-right sweep from a chosen point along the waveform you're looking at.

Never learned to make sense of a broken PLL without a 'scope. It's the swiss-army knife for that kind of task. A meter is fine for getting a precise reading of a steady voltage. But a PLL is full of things that are anything but steady. No other way to see what's going on in there that I know.

73