Ranger AR-3500 Receive Issue

D18 through D21 show on the schemo as type 1N60. They are germanium diodes, with a smaller voltage drop than the ubiquitous silicon 1N4148 diodes. Makes them more sensitive to a small signal. But the glass package they're in is larger than the silicon diodes, and subject to fracture. Just a gentle nudge sideways to each will reveal a broken part.

My first guess, anyway.

73

I have one (100w type) that has the opposite issue. It receives signals, but is otherwise deaf.

Far longer possible list of suspects. Alignment is step one to diagnose a deaf receiver. That, and a steady test signal strong enough to hear.

73

Time to follow the AM AGC voltage from where it starts. Need a steady test signal. A 'scope is best, but a voltmeter will do in a pinch. IC2 pin 5 is where the output of D18/D19 feed into next. Roughly double that DC voltage should come out of pin 7. The pin 7 output now goes into pin 12, and out pin 14 and into D25. Voltage coming out of D25 cathode (band end) should be about 6/10 of a Volt less than what went into it.

A lot of the stuff on that list would also screw up sideband receive.

And if the AGC voltage is not being lost in AM mode, I'm not sure what to blame.

73

AGC also taps the SQ line, does the Squelch work normally or is it totally useless in AM?

Then there may be the "Tap" to the S/RF meter circuit that comes off both SSB and the AM/FM side.

There are two caps that merge their detected signal together into one line - if one of the caps has failed - causes a dead short from the output on one side (AM/FM or SSB) to drown out the other.

So when you have AM "loudness" - check for SQ and if it seems to have normal operation- if ok - we can move to the AGC side and see if something there is not sensing and sending a correction signal to the gain of the AM/FM side or it's something further down the path of signal like the AF amp in overdrive. You Say SSB seems normal so kinda want to rule out the Audio Preamps at the moment - gawd hope this isn't a blown RF switch diode.

BTW - this also affects FM too.

These things are a lot like a Galaxy or Uniden Jackson - at least when it comes to the use of a Quad Op-Amp to handle S/RF - AGC and Squelch

Hello to all, I have a recieve issue also on my Ranger AR-3500 radio,maybe you could shed some light on what's going on, I have transmit with audio all bands, but there is no sound coming from internal speaker or when I hook up external speaker, nothing at all but a slight buzz from external speaker when volume is turned all the way up, I can see the meter moving when people are talking, i even hooked up another radio next to it with antennas into both radios and still nothing at all when I key the second radio, same slight buzz or hum from speaker, have you ever seen this issue before sir? Really would like to fix this relic, seems like a really nice radio any info is gold.
Thanks

nomadradio said:

D18 through D21 show on the schemo as type 1N60. They are germanium diodes, with a smaller voltage drop than the ubiquitous silicon 1N4148 diodes. Makes them more sensitive to a small signal. But the glass package they're in is larger than the silicon diodes, and subject to fracture. Just a gentle nudge sideways to each will reveal a broken part.

My first guess, anyway.

73

Click to expand...

NewHello Mr NomadRadio sir, I have a recieve issue also on my Ranger AR-3500 radio,maybe you could shed some light on what's going on, I have transmit with audio all bands, but there is no sound coming from internal speaker or when I hook up external speaker, nothing at all but a slight buzz from external speaker when volume is turned all the way up, I can see the meter moving when people are talking, i even hooked up another radio next to it with antennas into both radios and still nothing at all when I key the second radio, same slight buzz or hum from speaker, have you ever seen this issue before sir? Really would like to fix this relic, seems like a really nice radio any info is gold.
Thanks

Well ... I am biased on this but any radio with 40 year old electrolytics is time wasted when troubleshooting problems. Guess what, I have a kit for this radio. Who knew?

https://klondikemikescapkits.com/products/clear-channel-ranger-ar-3300-electrolytic-capacitor-kit

Good chance that Mike is right. You could poke an oscilloscope probe into each stage of receiver audio and follow the signal. A bad cap tends to make itself visible when a signal looks good on one side of the cap, and disappears where it should be coming back out the other side. This of course would confirm his prediction that a bad electrolytic cap is the culprit.

Or, for caps that serve to decouple signals to ground, you look to see a signal level that does NOT belong there.

But then you'd be tempted to replace only the one that checks bad today. And the radio will work, until the next one goes bad. Not a question of "if" but of "when".

We call that process "Electronic Whack-A-Mole". Eventually every one of the original electrolytics in the radio will die if you use it long enough.

Or you could replace them all, and forestall this problem for another 20 or 30 years before it happens again for the same reason a second time around.

The risk is that you'll replace all those capacitors, get it totally right with NONE of them turned around backwards, and no tiny bridges of solder across a gap between foil traces.

--And, find out that's not the whole problem.

Worst case, the radio still exhibits the same symptom that it did before.

But troubleshooting is a statistical sort of thing. The more data you gather about what's working and what's not, the smaller the risk of diagnosing it wrong.

And the less data you gather from the radio, the higher the chance your 'fix' won't clear the fault.

Kinda like the old carpenter said. "Measure once, cut twice, measure twice cut once."

73

I am glad I found this thread! I hope it's not too old to revive. I have 2 AR-3500 and 1 AR-3000 ALL with a "closed" squelch! All act the same ! What are the chances ?

S-meter moves, ect. no RX no static on FM, meters show incoming signal. Via SM I checked voltages. IC2 seems to have voltage where it shouldn't be.
Now, If I unsolder leg 8 of IC2 I get RX but, loose squelch function, and signals seem overloaded. I am lost in the squelch /AGC circuit on what part to go to.

I am in the process of electrolytic recap but I feel I diode or transistor is allowing voltage to pin 10 and 8 by 10 being hooked up. Voltage seems to be coming in on pin 10. R80 is allowing 7.8 from pin 4 That feeds from pin 4 power. R80 checks.

The voltages of pins IC2 (2902) :
mine (service manual voltage charts )
Normal voltages on pins1-6
Pin 7 .14v (1.64v)
Pin 8 6.5v (.01v) !!!!
Pin 9 1.8v (2.91v)
Pin 10 7.6v (2.42) !!!!
Pin 11 normal
Pin 12 .6v (1.52v)
Pin 13 .5v (1.5v)
Pin 14 1.5v (1.5v)

There is a squelch trim, so that uses R81 to sip off power from that 7.8 volts, it should be adjustable.

VR301 if my old scratchy schematic is correct.

Handy Andy said:

There is a squelch trim, so that uses R81 to sip off power from that 7.8 volts, it should be adjustable.

VR301 if my old scratchy schematic is correct.

View attachment 49785

Per what you claimed earlier, a recap may be all that is needed.​

Click to expand...

Well, Andy - you were right on VR301. This solved one of the issues ! The squelch knob, like many this age has gone bad moving it just right got audio. Maybe it was old enough to push the power back from the reset knob click giving me those voltages to short squelch. Bypassed knob for now. Mic gain was one a bit dirty, solved low audio issue I was having.
I have a cap kit on order just to get that done to eliminate that for possiable AGC issue, caps are 40+ old now. Anything would be worth troubleshooting further before that
This AGC issue, though,
Note, I can inject a signal from my R&S CMU200 1kHz tone @ 27.205 @ 100 % mod to the ANT jack and around -50dBm the radio hears about s7 then -46dBm Then starts with around S9 with distortion to a howl. On outside antenna it is what you've said before that about half way on RF gain the strong stations distort - very loud rx..

I have been reading up on your great posts and others on AGC / Op-Amps and functions on other radios and functions. Would the D18-D21 "front end protection diodes?" I just would like to grasp these concepts better. I do see some President Jackson AGC mods and you are right the concepts and layouts are very similar to this. I know this radio is long in the tooth before internet and these problems are a hassle in these older ones. I am used to those 2950 Service manuals with the flow charts with parts with them and the old 2sc2999 mods way back on cbtricks let you know what part did what in many radios, but see a bit of what I read you hope it wouldn't be switching diodes -that would be PIN-type D1, D2 ? I here are long from being made too.

I am still learning this equipment and I have an scope and a bag of new parts and a parts RCI2950mk2 this 1959y, 1n4148, 1n6263, 2902n. Shoulda went to school for this !