Galaxy Saturn EPT210011A Early frequency counter problem

[digitalwacker73]

Hoping someone on here can help me? Have an old Saturn that needed a frequency counter. Located one that was working for a fair price, but didnt work when I hooked it up to the radio. Have since noticed that the cable was plugged in backwards at the channel display/frequency counter. Which explains why the original counter was missing. At this point I want to pull my hair out. I have since corrected the cable issue, but obviously something must have shorted. I'm not getting correct voltage at the 7808 regulator and have tried replacing it, d603, and all the electrolytic caps. Hopefully it's repairable. Anyone in this forum willing to help? Thanks in advance!

 

[nomadradio]

I got in the habit of removing the 5-Volt zener and kluging a 7805T regulator across the holes for the zener's dropping resistor. Current drain wasn't high enough to require a heat sink on the 7805. And it was more reliable than the tiny zener.

Parts is parts. So long as the pc board still has foil traces it should be repairable. Hopefully the TC5032 chip is undamaged. That one gets harder to find as the years go by.

Never have learned to troubleshoot a counter without a 'scope.

73

 

[digitalwacker73]

I got in the habit of removing the 5-Volt zener and kluging a 7805T regulator across the holes for the zener's dropping resistor. Current drain wasn't high enough to require a heat sink on the 7805. And it was more reliable than the tiny zener.

Parts is parts. So long as the pc board still has foil traces it should be repairable. Hopefully the TC5032 chip is undamaged. That one gets harder to find as the years go by.

Never have learned to troubleshoot a counter without a 'scope.

73

I got in the habit of removing the 5-Volt zener and kluging a 7805T regulator across the holes for the zener's dropping resistor. Current drain wasn't high enough to require a heat sink on the 7805. And it was more reliable than the tiny zener.

Parts is parts. So long as the pc board still has foil traces it should be repairable. Hopefully the TC5032 chip is undamaged. That one gets harder to find as the years go by.

Never have learned to troubleshoot a counter without a 'scope.

73

I'm assuming you are referring to the 2.4v zener?

I got in the habit of removing the 5-Volt zener and kluging a 7805T regulator across the holes for the zener's dropping resistor. Current drain wasn't high enough to require a heat sink on the 7805. And it was more reliable than the tiny zener.

Parts is parts. So long as the pc board still has foil traces it should be repairable. Hopefully the TC5032 chip is undamaged. That one gets harder to find as the years go by.

Never have learned to troubleshoot a counter without a 'scope.

73

Thank you for taking the time to respond.
Are you referring to the 2.4v zener? I cant figure out why I'm receiving over 10v on pin 3 of the 7808. Even stranger I'm getting voltage on the center pin which should be ground. I've even removed one leg of all parts connected to pin 3 to see if I get 8v, with no change. At this point might be cheaper and easier just to search for another counter module. I'm sure I'll continue to troubleshoot with my limited means.

 

[999]

I'm assuming you are referring to the 2.4v zener?


Thank you for taking the time to respond.
Are you referring to the 2.4v zener? I cant figure out why I'm receiving over 10v on pin 3 of the 7808. Even stranger I'm getting voltage on the center pin which should be ground. I've even removed one leg of all parts connected to pin 3 to see if I get 8v, with no change. At this point might be cheaper and easier just to search for another counter module. I'm sure I'll continue to troubleshoot with my limited means.

If that happens, let me know. I have one that works, but has been in a drawer for 10+ years. I tested it yesterday and it flashes all over the place when I first turn it on, but within 30 seconds it's rock solid on frequency.
I ordered new electrolytic caps for it today as I figure that is where the issue is and will have them next week.
I left it on overnight to make sure that it doesn't have the overheating issue where it starts to drift or shut off, and it doesn't.

 

[digitalwacker73]

If that happens, let me know. I have one that works, but has been in a drawer for 10+ years. I tested it yesterday and it flashes all over the place when I first turn it on, but within 30 seconds it's rock solid on frequency.
I ordered new electrolytic caps for it today as I figure that is where the issue is and will have them next week.
I left it on overnight to make sure that it doesn't have the overheating issue where it starts to drift or shut off, and it doesn't.

How much?

 

[nomadradio]

Are you referring to the 2.4v zener?

Ummm, yeah. Brain fart. The 2.4V zener is there to drop 8 Volts down to just over 5 Volts. It's not a "5-Volt zener" like I said.

Your experience with the 7808 suggests bad or broken traces on the pc board. Pursuing a "new" counter module that still works may be the shorter route to the result you want.

If the 5-Volt parts received excessive supply voltage, you could have a laundry list of chips that have to be replaced. Pretty hard to justify that much work and expense if you can solve the problem a simpler way.

73