Icom ic-2500/1500

[byndhlptom]

I have several 2500s and a 1500 that are not staying on frequency. They show as fluctuating signal strength, with the audio working at upper levels. Acts like the PLL is not locking..... across all frequencies, (main rx for 2500)

The service manuals I have found make no reference to PLL alignment. The also assume that you have the remote head (all instructions reference control panel controls). Is there a set of alignment instructions for the PCR series I just have not found yet? The alignment instructions do not show what to adjust for the various steps, just settings and acceptance commands.

Any suggestions?

I have access to all listed test equipment..... and know how to use them

 

[Ubbe]

I think it's a voltage regulator problem with these units. Maybe bad caps somewhere. I have a R2500 that suddenly refused to power on. There where some kind of high current draw that made the power on circuit malfunction. Then suddenly after 6 months it did power on and worked for a few weeks and then the BFO stopped working.

I look in the schematics and there's no adjustment anywhere for VCO or PLL. I suggest you check that the voltages are all ok from the different regulators. It's one common TXCO for both the A and B receiver in a R2500 and your B receiver are working ok so it couldn't be the master oscillator drifting.

You have those two "Icom R2500service" pdf files?

/Ubbe

 

[byndhlptom]

Thanks for the information.

I have several files I have found. They are all 8K plus in size. Not sure if they are the two "Icom R2500service" files you are referencing......

" there's no adjustment anywhere for VCO or PLL "

I came to the same conclusion after looking at schematic. Checking voltages was where I am starting.... hopefully the problem is there and easily fixed. I am assuming that like the 1000, they have a special program that allows changing EEPROM data for tuning (or something like that)

The two 2500s B sides are both working, only the A sides are flaky.

I will let everyone know what works (or not!).

 

[Ubbe]

I would take a look at C335 C336 that are polarised and connected in series in the loop filter from the PLL. It's a risk that one cap will be polarised the wrong way and after some time it will fail.

You probably have the schematics you'll need but one pdf are 3MB and the other almost 5MB so could be some more text info included that might be useful.

Icom R2500service_1of2.pdf

drive.google.com

Icom R2500service_2of2.pdf

drive.google.com

/Ubbe

 

[byndhlptom]

Just saw your reply....I will look at the caps....

I had one of your files, not the other....

thanks!