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dx2517 voltage regulator

ira parker

Member
Apr 18, 2015
22
13
13
65
Having issues with the 8 volt rail. It has the sa1869 regulator in it 2.4 volts on the collector when attached lift the leg it goes to 13 volts, removed it tested it on 2 different testers show good no leakage? I've tested components before that showed good when in fact they were faulty! If I replace the regulator is the sa473 better or what's a good upgrade when I upgrade the sb754 I always upgrade the companion part to the sa1012. I've started testing components working back to the mod regulator but my mind keeps thinking about the 13 volts on the 1869 with the collector lifted, any thoughts or suggestions greatly appreciated. thanks Ira
 

q35 tested good, haven't pulled the diodes yet I started with the electrolytic caps first but I didn't think the regulator should be 13 volts on the collector when lifted just wanted to verify my starting point was good before continuing. Wasn't sure if the circuit pulls that 13 volts down to 8 volts or if the regulator was actually bad, I have some used 1869s and some new sa1012s and maybe a sa473 didn't want to ruin a new regulator if there is a short in circuit. second guessing myself and maybe save some extra work.
 
q35 tested good, haven't pulled the diodes yet I started with the electrolytic caps first but I didn't think the regulator should be 13 volts on the collector when lifted just wanted to verify my starting point was good before continuing. Wasn't sure if the circuit pulls that 13 volts down to 8 volts or if the regulator was actually bad, I have some used 1869s and some new sa1012s and maybe a sa473 didn't want to ruin a new regulator if there is a short in circuit. second guessing myself and maybe save some extra work.
817,1012 mod regs test good 2003v 5 pin mod amp replaced with a new one lifted all legs on the irf520s removed shorting board then found the issue with the 8 volt rail have tested about half of the electros and ceramic caps working back to the mod regulators.
 
817,1012 mod regs test good 2003v 5 pin mod amp replaced with a new one lifted all legs on the irf520s removed shorting board then found the issue with the 8 volt rail have tested about half of the electros and ceramic caps working back to the mod regulators.
Update the puppet master does it again zener was bad now have 8.6 volts on the rail. You da man now I can start checking everything else out. Thank you so much man I love this site. thanks Ira
 
Rock on! Gotta love it when a plan comes together.

I lost patience with that regulator circuit a while back and bought some 7809T regulator chips. The legs get 'crossed' to put it in place of the original transistor, but it solves the problem with minimum rabbit-hole time.

This pic shows a 7808T with a diode between the center pin and the radio's ground foil. Boosts the 8 Volts back up to the 8.7 or so the original regulator delivers.

ept36009vregsubsm.jpg


Just saves labor compared to troubleshooting the factory circuit. And if you can get the all-plastic version instead of the one with the metal tab you can skip the insulator and bolt it directly to the heat sink.

73
 
2sa1869 is up to 3A , 7808 is just 1A. Is it enough in that case?
Mike
I thought about a 2sa1012 that you use for the sb817 companion since a lot of the sb754 had 1869 as the companion. Any thoughts? Does anyone have a tr/ic voltage chart for this 690011d board. As you know i got the 8 volt up and going did a partial alignment mainly pll alignment everything looks good tx/rx light is switching so I'm assuming its locking, but no signal on monitor radio or meter (receive is working and spot on freq) tested the irf520s there good haven't checked the pre drivers yet. Sniffer from monitor radio to the tab of the 520s shows a weak signal on monitor. I can adjust the voltage at the shorting board via the vr and it steps to 13v for ssb sure would like a voltage chart for this board or another model with mosfets. Thanks Ira
 
Voltage chart? Yeah, that's a lost art. For all the info posted for the old and new 2517 at CB Tricks, that's the one thing missing.

If you haven't tried alignment, that would be next. Even if you are sure that no golden screwdrivers have been in there, it's worth checking. A tuning slug that won't peak properly points to a fault in that circuit.

73
 
7808 is just 1A.
If you could look up the current rating of the output transistor inside a 7808T, I suspect that it's at least 3 Amps. Typical rule for a power supply regulator is to allow for temperature rise. Get the 3-Amp transistor hot enough, and it's only rated for 1 Amp. Spec sheets often include a chart showing the power-dissipation rated compared to its internal temperature.

And this is the beauty of the 780x-family of regulators. They limit current and temperature, usually enough to prevent suicide. The radio should never see more than a half an Amp draw from the 9-Volt supply even with a counter display running from it. The factory regulator circuit is suicidal if you overload it.

73
 
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Voltage chart? Yeah, that's a lost art. For all the info posted for the old and new 2517 at CB Tricks, that's the one thing missing.

If you haven't tried alignment, that would be next. Even if you are sure that no golden screwdrivers have been in there, it's worth checking. A tuning slug that won't peak properly points to a fault in that circuit.

73
2517 update. It's alive!!! I had aligned the pll section, all good. Then nomads post got me thinking I had 0 watts on the meter but I could see a little signal on the monitor radio with the sniffer hooked up so clipped the sniffer on one of the coils and ran the pa section alignment all pots responded with good peaks, still no watts at the meter. Light bulb in the head went off and ah ha moment (check for output frequency) sure enough 9. something mhz starting checking the crystals and the 10.685mhz had one off the legs ate into from my favorite brown glue crude crap. decided to remove all of them and check for the infamous brown crud and sure enough the 10.240 suck one of the legs up in the desoldering gun and the 14 mhz was almost ate into replaced all three and bingo up and running full output took the alignment very well. So anyone reading this or following the progress will understand the damage that stuff does as it ages it also becomes conductive. 1st priority dig all that crap out and start over. Once again gentlemen thanks for your support did I mention I love this site!! Thanks Ira
 
2517 update. It's alive!!! I had aligned the pll section, all good. Then nomads post got me thinking I had 0 watts on the meter but I could see a little signal on the monitor radio with the sniffer hooked up so clipped the sniffer on one of the coils and ran the pa section alignment all pots responded with good peaks, still no watts at the meter. Light bulb in the head went off and ah ha moment (check for output frequency) sure enough 9. something mhz starting checking the crystals and the 10.685mhz had one off the legs ate into from my favorite brown glue crude crap. decided to remove all of them and check for the infamous brown crud and sure enough the 10.240 suck one of the legs up in the desoldering gun and the 14 mhz was almost ate into replaced all three and bingo up and running full output took the alignment very well. So anyone reading this or following the progress will understand the damage that stuff does as it ages it also becomes conductive. 1st priority dig all that crap out and start over. Once again gentlemen thanks for your support did I mention I love this site!! Thanks Ira
One other thing, in doing these alignments I always have an issue reading the oscillator frequency on tp6 for the ssb. So I use my hf rig and tune them by ear then get one of my buddies with a waterfall on the radio to come check my signal and fine tune it to spot on. Is there a secret to getting my freq counter to read at test point 6?
 
That glue is why I started to recap old radios as a matter of course. Since I have to pull the big caps anyways to get that crud out, might as well finish the job.

Good on you for sticking with it and getting the radio working again.
 
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I use my hf rig and tune them by ear

We use a 1 kHz audio oscillator, and tune the receiver 1 kHz above the desired frequency set to LSB. The heterodyne tone from the speaker will be exactly 1 kHz when the test signal is right. The audio beat note you'll hear from the two tone sources will get you within 1 Hz. Much better than trying to "zero beat" using a radio with no bass response to the receiver audio.

73
 
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