General Stonewall Jackson Power supply help

[KD2GOE]

i'm working on a General Stonewall Jackson for a friend it needs a new set of 2n3771 not a big dead i have them but on the supply board are 2sb827 transistor and a KA7808 transistor
the radio has the same PSU as the RCI-2990 and the saturn galaxy turbo..
i cant fined the schematic for the psu some one was dicking around in here before me and i want to make sure i put the right things back in..

 

[KD2GOE]

never mined i got it the KA7808 8volt reg was bad..

 

[loosecannon]

you can make life easier on both of you if you just replace that monstrosity with one of these:
https://www.ebay.com/itm/36-Amp-10-...ZbFgu-:sc:USPSPriorityFlatRateBox!89108!US!-1

soooo much lighter, and more efficient too.
you just need to put that 7808 in circuit and you're off to the races.

the owner will thank you for putting his radio on a diet that resulted in losing 10lbs.
LC

 

[nomadradio]

We have used the cheaper chinesium 30-Amp versions from chinaBay with good luck so far.

The factory supply has no current limiting. As a result, it's vulnerable to damage. Also it has no protection from excess output voltage. Our experience was that sooner or later one of the 2N3771 would short, shooting unregulated 24 Volts into the radio, typically croaking the front-panel computer.

The Megawatt supply is fully protected both ways. Haven't tried one of those yet, so I'll have to take someone else's word that it fits where the 30-Amp versions will go.

Due to the reliability issues with the older power supply we replace it with a 30-Amp rated switchmode "brick" any time it causes trouble in a customer's radio. I don't need the headache of a radio that fails after it goes home.

In fairness, the cheaper chinese supplies sometimes fail new out of the box. We buy them 4 or 5 at a time and test before installing in a customer's radio. The occasional dud raises the overall cost, but the lower price keeps the price of repair jobs down. So far we haven't had any of them fail in the customer's radio, so long as we test it before it's installed.

If you're maintaining your own radio, the more-expensive Megawatt supply is the safer bet, less likely to cause you trouble. The economics of fixing just one radio is a bit different from fixing a dozen of them.

There is one odd symptom we have seen from the factory supply with the heavy transformer. The lights would flash brighter than normal, just briefly when the mike is unkeyed. Never did get to the bottom of what causes this. We did learn that it's a warning from the regulator circuit that a breakdown is coming soon. If you see the radio do this, pull the plug from the wall until you can install a switchmode brick. That brief flash is a warning that the regulator will fail and run away, shooting unregulated voltage into the radio some time soon.

There is one safety measure we install in the 'big' black radios no matter what. A fuse in line with the power wire to the radio pc board. You wouldn't power a 5-Amp mobile radio from a 25-Amp power supply without a fuse, right? But that's what's inside that cabinet as it comes from the factory. Not exactly russian roullette, but close enough.

73

 

[sonoma]

I have been installing the little 10 amp units in the cobra 142 and washington radios when needed. I have 2 new ones here right now plus a 30 amp unit for a high output radio. they have worked just fine so far. have not had one to fail.

 

[nomadradio]

Had one Chinabay brick bad out of the box. Never did try to find out why. Another one was DOA, but turned out to be a poorly-soldered 120/240 select switch. Simple fix, worked fine after that. Another one wouldn't start its internal fan. Just sent that one to the e-cycle, wrote it off.

Murphy's Law would suggest that if you only buy one, you are far more likely to get a dud. In a typical order of four or five units, we see about one dud out of ten.

Not a terrible percentage. Only raises the cost of the other nine units by ten percent if we just chuck the dead one and write it off.

And if you only need one, I still say the Megawatt is the safer bet. At least there is someone to complain to if you had any trouble. The aggravation you would avoid looks to me well worth the additional price.

73

 

[KD2GOE]

you can make life easier on both of you if you just replace that monstrosity with one of these:
https://www.ebay.com/itm/36-Amp-10-...ZbFgu-:sc:USPSPriorityFlatRateBox!89108!US!-1

soooo much lighter, and more efficient too.
you just need to put that 7808 in circuit and you're off to the races.

the owner will thank you for putting his radio on a diet that resulted in losing 10lbs.
LC

I would have 100% did that if the guy wanted to spend the money..
i even told him about doing that..
So what i did is turn it down to just 100W SSB and 25/100 on AM and put a computer fan to cool it down for him..

We have used the cheaper chinesium 30-Amp versions from chinaBay with good luck so far.

The factory supply has no current limiting. As a result, it's vulnerable to damage. Also it has no protection from excess output voltage. Our experience was that sooner or later one of the 2N3771 would short, shooting unregulated 24 Volts into the radio, typically croaking the front-panel computer.

The Megawatt supply is fully protected both ways. Haven't tried one of those yet, so I'll have to take someone else's word that it fits where the 30-Amp versions will go.

Due to the reliability issues with the older power supply we replace it with a 30-Amp rated switchmode "brick" any time it causes trouble in a customer's radio. I don't need the headache of a radio that fails after it goes home.

In fairness, the cheaper chinese supplies sometimes fail new out of the box. We buy them 4 or 5 at a time and test before installing in a customer's radio. The occasional dud raises the overall cost, but the lower price keeps the price of repair jobs down. So far we haven't had any of them fail in the customer's radio, so long as we test it before it's installed.

If you're maintaining your own radio, the more-expensive Megawatt supply is the safer bet, less likely to cause you trouble. The economics of fixing just one radio is a bit different from fixing a dozen of them.

There is one odd symptom we have seen from the factory supply with the heavy transformer. The lights would flash brighter than normal, just briefly when the mike is unkeyed. Never did get to the bottom of what causes this. We did learn that it's a warning from the regulator circuit that a breakdown is coming soon. If you see the radio do this, pull the plug from the wall until you can install a switchmode brick. That brief flash is a warning that the regulator will fail and run away, shooting unregulated voltage into the radio some time soon.

There is one safety measure we install in the 'big' black radios no matter what. A fuse in line with the power wire to the radio pc board. You wouldn't power a 5-Amp mobile radio from a 25-Amp power supply without a fuse, right? But that's what's inside that cabinet as it comes from the factory. Not exactly russian roullette, but close enough.

73

I 100% agree with you..

 

[KD2GOE]

I have been installing the little 10 amp units in the cobra 142 and washington radios when needed. I have 2 new ones here right now plus a 30 amp unit for a high output radio. they have worked just fine so far. have not had one to fail.

can you send me a link to that???

 

[sonoma]

I just go to the auction site and put in what I want and see what shows up. I have not bought any in a long time since I had bought a few some months back. I will see what they have available.

 

[sonoma]

here is what I look for to buy a 10 amp supply. you may want to ask the seller if they will go up to 13.8 volts also. I bought some that would only go to 12.8 volta one time. so look at what all is available.

https://www.ebay.com/sch/i.html?_fr...supply.TRS0&_nkw=10+amp+power+supply&_sacat=0

 

[sonoma]

forgot to mention most are about the size of 2 packs of cigs put together so they fit just fine inside the radio.
https://www.ebay.com/itm/DC-12V-3A-...hash=item1cc43c6e78:m:mzpSnaqRQnafbF-chvQlS3g

 

[Shadetree Mechanic]

I just go to the auction site and put in what I want and see what shows up. I have not bought any in a long time since I had bought a few some months back. I will see what they have available.

I have looked at these but don't want to get something that has RF noise. Have you had any problems with this?

 

[sonoma]

never had one give out any rf noise. I have installed about 8 of them so far.
Nomad does more repairs than I do so he may chime in if he has a problem with any other than not working.

 

[KD2GOE]

I have looked at these but don't want to get something that has RF noise. Have you had any problems with this?

that's what i am saying i have ordered a few 12v PSU's and had RF Noise...
the only one i was good on was the megawatt PSU's

 

[nomadradio]

I have learned to route any wires leading to or from a switchmode brick away from the antenna socket and the receiver's antenna stages. Even a supply with good filtering can radiate noise from either the AC power input or the DC output wires if they are close enough to a sensitive circuit.

In some radios we have seen a ceramic disc cap placed across the + and - screws on the brick's barrier strip. Maybe it's just luck, but we haven't found a need for that.

Yet.

73