more complete and simplified HR2510 PLL alignment?

[Jason Bowers]

Been over thirty years since I was active on 10 meters (and that long since I was active on any radio!). I have a pair of 2510's, unmodified, and talked the world on 10 in the early 90's. Put them away until my interest was sparked recently by some 10 meter activity. So, brought out the pair I had in storage. One I bought brand new. The mic plug retention ring was loose and trying out the radio I determined why: no modulation. Turned out to the the mic element itself. Replaced and all go. This radio, which I'll call #1, seems good to go now.

Now the problem one, radio #2. I bought this one from someone and they apparently tried to do something with the frequency range. I noticed right away on the processor/ PLL board that the 22 Mhz crystal was missing, so replaced that. Wouldn't lock on anything, then noticed a cap from the top of TP306 to ground and a couple of parallel caps on the bottom of L304. I removed those and the radio then seemed to lock, somewhat at least. A couple of questions:

1) In the service manual, it says using an oscilloscope while making adjustments to the various coils of the PLL, but specifies frequency values. Is it possible to just use a frequency counter for those test points? Unfortunately, I no longer own a scope.

2) It appears to be that a couple of coils not specified in the manual were adjusted, particularly L304 and L310/319. Any ideas as to what to monitor here for adjustment would be welcome.

Thanks!

2)

 

[Low_Boy]

I would use a frequency counter for question #1
I have had a lot of HR2510's but have never touched L310 or L319. If you turn something on that board the wrong way you can open up a whole new can of worms.
My Thoughts.

 

[Jason Bowers]

Thanks, and ok for that. I'll use the counter.

Well, worse comes to worse, I can set both radios up and use the known good one as a reference while I make adjustments. I did switch out the microprocessor boards to make sure the tinkered radio didn't need adjusted for the other circuitry and all checked out well.

I think the L310/319 coils might have something to do with output from the board. I noticed while adjusting them that my transmitter output increased beyond the specs (about 15 watts Am/ 32 watts SSB), so I suppose I could readjust those until power is the same as the untinkered unit. Sill not sure about L304 though.

 

[Low_Boy]

I would not touch L304.

 

[Jason Bowers]

Well, I found some info from Rogerbird's site on L310 and 319. One being adjusted for high band, the other low band.

I realigned it today using frequency counter and DVM as per the Uniden SM. Compared with my fully working unit. Went ok, but I am noticing that I appear to be losing about half of the bandwidth. In other words, the PLL seems to lose lock. As I said before, this radio is unmodified so would normally cover 28-29.7, but I can only get from about 28.9 to 29.7. Nothing I do with the adjustments can restore the lock for any further range. Not sure what's going on, any insight welcome.

 

[Dr_DX]

Is radio #2 Chipswitched?

If not, try adding a cap here:



and see if it will now lock up on a lower frequency.

Using a watt meter and dummy load, set the radio to the upper limit of the operating range and adjust L310 for max power out. Set the radio to the lowest frequency that it will lock and adjust L319 for max power out. Then see if it will lock at a lower frequency and adjust L319 again for max power out. Repeat until you get it to lock on 28.000 and adjust L319 for max power out.

 

[Rogerbird1]

Thanks, and ok for that. I'll use the counter.

Well, worse comes to worse, I can set both radios up and use the known good one as a reference while I make adjustments. I did switch out the microprocessor boards to make sure the tinkered radio didn't need adjusted for the other circuitry and all checked out well.

I think the L310/319 coils might have something to do with output from the board. I noticed while adjusting them that my transmitter output increased beyond the specs (about 15 watts Am/ 32 watts SSB), so I suppose I could readjust those until power is the same as the untinkered unit. Sill not sure about L304 though.

L304 is used to adjust a stage of the mixer IC.
You should be able to scope a sine wave on the inputs or outputs of the halves of each mixer - S042P (one pin will have a mix the other will have a clean sine wave):
L303 pin 11 or 13 of ic304 and pin 7 or 8 L304 (output 10 or 12 / 2 or 3)
L313 pin 11 or 13 of ic305 and Pin 7 or 8 on L314 (output 10 or 12 / 2 or 3)
Which ever pin you can get the best signal on and adj the coils for max signal P-P
I would do this at 28.000Mhz with the RIT in the center.

There are lots of undocumented adjustments on the PLL board.. proceed with caution.
Roger