Here's a video on where to find the gears. I've done this a few times. The only thing I had to do was to open up the hole just a little in the one gear so it would slide over the shaft. I bought the timers from eBay for about $8.00 each.
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Junker 858 Madison
- Thread starter TM86
- Start date
Ordered a gear set from him this morning. He claims he's pretty quick with shipping, we'll see.
Looks like the clock gears will be in the mail come Monday.
Decided after cleaning up TR402 and TR403 and putting silpads behind them I might as well get the AM regulator, driver, and final as well. Glad I did.
The final was kind of nasty looking on the solder side, with the cruft from previous solder jobs thick enough that I couldn't see the separation between traces. Cleaned that up and found that chunks of the traces for the emitter and base were missing. The emitter was easy in that the lead was long enough to reach over to where it needed to go to make a connection. The base, not so much. There was a component lead poking through the board with no copper around it. Grabbed a little copper donut and used the final's base lead to hold it down and connect it to the rest of the trace like it used to be.
Finished removing the glue, I hope. Squeezed a few coils back together. Replaced the meter lights and unlike the last guy in here I insulated the connections, so the radio is less of a fire hazard than it used to be.
Opened the SWR/MOD meter to see how stuck it was. Movement seemed to turn pretty freely. Checked it with an ohmmeter, open circuit. Probably not a good thing. Guess I'll head over to Barkett's and order one.
Decided after cleaning up TR402 and TR403 and putting silpads behind them I might as well get the AM regulator, driver, and final as well. Glad I did.
The final was kind of nasty looking on the solder side, with the cruft from previous solder jobs thick enough that I couldn't see the separation between traces. Cleaned that up and found that chunks of the traces for the emitter and base were missing. The emitter was easy in that the lead was long enough to reach over to where it needed to go to make a connection. The base, not so much. There was a component lead poking through the board with no copper around it. Grabbed a little copper donut and used the final's base lead to hold it down and connect it to the rest of the trace like it used to be.
Finished removing the glue, I hope. Squeezed a few coils back together. Replaced the meter lights and unlike the last guy in here I insulated the connections, so the radio is less of a fire hazard than it used to be.
Opened the SWR/MOD meter to see how stuck it was. Movement seemed to turn pretty freely. Checked it with an ohmmeter, open circuit. Probably not a good thing. Guess I'll head over to Barkett's and order one.
Ah, donuts. Is there nothing they can't do?
One of these little guys: https://www.elliottelectronicsupply.com/copper-foil-donuts.html
I think I figured out the clarifier. It looks like whoever did the clarifier mod originally had soldered a wire to the cathode of D44, a 9 Volt zener diode. That's the wire I found one end floating in the chassis. I pulled that wire under the board and soldered it to the positive side of C135, which is also connected to D44. Funny thing is, if the original guy had done this he would have found that the wire he used was the perfect length to pull through the retaining clips around the edge of the board and reach where it's now soldered. 
Did 399's power relay mod, since I was in there. Thanks, JJ!
On a parts hold for at least a few days. Got bits coming for the clock, the dead meter, the two inductors that are missing, and the big cap in the power supply.
Oh, and a new soldering iron. Mine literally fell apart. Metal bits just slid right off the ceramic element and onto the workbench. It's somewhat inconvenient when that happens. Eh, what did expect for 10 bucks?
Did 399's power relay mod, since I was in there. Thanks, JJ!
On a parts hold for at least a few days. Got bits coming for the clock, the dead meter, the two inductors that are missing, and the big cap in the power supply.
Oh, and a new soldering iron. Mine literally fell apart. Metal bits just slid right off the ceramic element and onto the workbench. It's somewhat inconvenient when that happens. Eh, what did expect for 10 bucks?
i've been using one of these at work for almost a year now and it seems to be holding up ok. definitely not for all day every day soldering, but for the price it does its job quite well.
New clock gears showed up today. Installed the new ones and the clock ran backwards. Reinstalled them the right way, and now the clock works as it should.
New meter showed up from Barkett's. They ship them in little cardboard boxes now to avoid them being crushed like the first set I ordered 9 or more years ago. Anyway, not quite an exact match, as the little plastic pegs that the SWR/MOD plate goes on are spaced differently. I just used the old front and the new back to work around that little problem. Couple of dabs of glue to hold the meter scale in place and it looks pretty good.
One other thing is that the new meter has an orange/red needle where the old one was white. Guess I'll just tell everybody it's because the modulation is so hot.
One other thing is that the new meter has an orange/red needle where the old one was white. Guess I'll just tell everybody it's because the modulation is so hot.
Box from Mouser finally showed up today. Installed big cap for power supply, did a modest upgrade to from 3300 to 4700 uFd. Replaced the two resistor bodge with a 5 Watt 220 Ohm unit. Installed the new L10 and L11 inductors and the new audio amp chip. Audio is working!
But now it only puts out a tiny AM signal and nothing on sideband. So I'm going to have to track that down since sideband was working so obviously I screwed up somewhere. But at least that tiny AM signal is being modulated. As in I can hear it on another radio.
Since LC asked, here's the part numbers I used for the inductors:
L10, 56 uH, Bourns part number RLB0193-563K
L11, 68 uH, Bourns part number RLB0913-683K
In my excitement I forgot to measure their DC resistance to see if they're anywhere close to 40 Ohms like the Sam's calls out. A quick interwebs check shows them to be about 150 Ohms, so only a little over three times the original value if Sam's got it right.
But now it only puts out a tiny AM signal and nothing on sideband. So I'm going to have to track that down since sideband was working so obviously I screwed up somewhere. But at least that tiny AM signal is being modulated. As in I can hear it on another radio.
Since LC asked, here's the part numbers I used for the inductors:
L10, 56 uH, Bourns part number RLB0193-563K
L11, 68 uH, Bourns part number RLB0913-683K
In my excitement I forgot to measure their DC resistance to see if they're anywhere close to 40 Ohms like the Sam's calls out. A quick interwebs check shows them to be about 150 Ohms, so only a little over three times the original value if Sam's got it right.
Still going in circles on this thing. One thing I've found is that I'm seeing about 750 mV P-P max for the VCO output on TP8. I've compared this to another 858 radio and that has about 1.1 V P-P. Which has me questioning if the 750 mV signal is OK or if it may be a problem.
The reason I'm looking in these places is that even though I do see a signal all the way down the TX chain as far as the base of the driver, it just seems like the amplitude of that signal is very small in comparison to a reference radio. And that smallness seems to start with the VCO output.
So I'll throw this out to the site. Is 750 mV too low a level out of the VCO to properly drive G2 on FET7, or should I pull my head out and start looking elsewhere?
The reason I'm looking in these places is that even though I do see a signal all the way down the TX chain as far as the base of the driver, it just seems like the amplitude of that signal is very small in comparison to a reference radio. And that smallness seems to start with the VCO output.
So I'll throw this out to the site. Is 750 mV too low a level out of the VCO to properly drive G2 on FET7, or should I pull my head out and start looking elsewhere?
Can you hear this radio's transmit on another radio? The signal level you saw should travel across the room and be heard. Odds are it would get louder when the scope probe touches the spots where you saw a transmit signal. If not, this suggests a PLL issue.
If the frequency the VCO is delivering is far enough out in left field, that can reduce the local-oscillator level. TP8 isn't connected directly to the tuned circuit on the VCO's output, so maybe it's not supposed to be affected the way any test point downstream from L16 would be affected.
I would be wondering about the actual VCO frequency you're getting. If it's beyond the PLL's lock range, odd things happen.
I'm used to watching TP7 on a 'scope. They give you a meter reading to set L17, but if the tuning voltage is showing dynamic behavior, a meter will never reveal this. Tuning voltage that oscillates will produce odd symptoms.
L24 almost never goes bad, but if it does you'll have problems getting it to lock properly. TP6 is what you watch to peak the two slugs. And if either slug exhibits the "slug flush with the hole's rim" symptom, that means L24 isn't actually achieving a resonant peak.
I won't bore you with the background of that quirk, but if you see it, you'll need to get L24 to a resonant peak on both slugs before the PLL will properly come back to life.
If the frequency the VCO is delivering is far enough out in left field, that can reduce the local-oscillator level. TP8 isn't connected directly to the tuned circuit on the VCO's output, so maybe it's not supposed to be affected the way any test point downstream from L16 would be affected.
I would be wondering about the actual VCO frequency you're getting. If it's beyond the PLL's lock range, odd things happen.
I'm used to watching TP7 on a 'scope. They give you a meter reading to set L17, but if the tuning voltage is showing dynamic behavior, a meter will never reveal this. Tuning voltage that oscillates will produce odd symptoms.
L24 almost never goes bad, but if it does you'll have problems getting it to lock properly. TP6 is what you watch to peak the two slugs. And if either slug exhibits the "slug flush with the hole's rim" symptom, that means L24 isn't actually achieving a resonant peak.
I won't bore you with the background of that quirk, but if you see it, you'll need to get L24 to a resonant peak on both slugs before the PLL will properly come back to life.
TP7 is on the scope right now. It's steady at about 2 Volts DC.
Hooked TP8 up to a counter, it's been steady at 34.9850 for at least 30 minutes. Which is what it should be for channel 19. Good thing that's what it's set for.
I can hear this radio on a monitor radio. So I should have thought that through better. If I can hear it that means I'm on frequency, or at least close to it. Which also tells me FET7 is doing it's job and is getting really annoyed with me poking it's legs with the scope probe.
So it would appear that what I really should be doing is looking at the driver and final to see what I may have screwed up when cleaning up the glob job soldering that was there when I started swapping in the silpads. It's possible the little copper donut I added to replace a burned off trace is touching something it shouldn't be. Didn't seem to be when I eyeballed it, but it won't hurt to look at it again.
Whatever it is, it appears to be somewhere between the output of FET7 and the antenna connector, so that narrows it down a little.
Hooked TP8 up to a counter, it's been steady at 34.9850 for at least 30 minutes. Which is what it should be for channel 19. Good thing that's what it's set for.
I can hear this radio on a monitor radio. So I should have thought that through better. If I can hear it that means I'm on frequency, or at least close to it. Which also tells me FET7 is doing it's job and is getting really annoyed with me poking it's legs with the scope probe.
So it would appear that what I really should be doing is looking at the driver and final to see what I may have screwed up when cleaning up the glob job soldering that was there when I started swapping in the silpads. It's possible the little copper donut I added to replace a burned off trace is touching something it shouldn't be. Didn't seem to be when I eyeballed it, but it won't hurt to look at it again.
Whatever it is, it appears to be somewhere between the output of FET7 and the antenna connector, so that narrows it down a little.
Finally got to spend a little more quality time with this radio tonight. I kept coming back to FET7. The output just seemed low to me, but I couldn't figure out why because all of the voltages looked correct.
On a whim, decided to see if I could improve the output by tweaking the input. Specifically, 7.8 MHz. And found that L39 had a cracked core. Swapped the core out, peaked the input to FET7, and found that output had greatly improved. Good thing I had a spare. Tweaked L39 and brought it up a little bit more.
It's moving the wattmeter just a tiny bit. But I have almost doubled the signal hitting the monitor radio. From S4 to a bit over S7. It looks like there's signal getting through the final and driver, but apparently not enough. That, or it is enough and not getting to the coax connector.
One step closer, anyways.
On a whim, decided to see if I could improve the output by tweaking the input. Specifically, 7.8 MHz. And found that L39 had a cracked core. Swapped the core out, peaked the input to FET7, and found that output had greatly improved. Good thing I had a spare. Tweaked L39 and brought it up a little bit more.
It's moving the wattmeter just a tiny bit. But I have almost doubled the signal hitting the monitor radio. From S4 to a bit over S7. It looks like there's signal getting through the final and driver, but apparently not enough. That, or it is enough and not getting to the coax connector.
One step closer, anyways.
- No one is chatting at the moment.
