International Crystal inc. Executive CTZ-100C no High Voltage

[Crambone]

I have a Executive that isn't showing any high voltage at the Filter Caps 100/100 500V , I disconnected the leads and the Caps test good. Looking at the schematic were should I start to look for my High Voltages?

Some voltages I tested.

Filter Caps both 0.0 Vdc

Converter Circuit:
Pin 4 13 Vac
Pin 5 7 Vac
Pin 6 O V

I.F. Unit
Pin 16 0 V
Pin 21 13 Vac
Pin 22 7 Vac

Audio Unit
Pin 33 & 35 0 V
Pin 36 12Vac
Pin 37 7Vac



http://www.cbtricks.com/radios/international_crystal/ctz_100c/graphics/ctz_100c_sch.pdf

 

[nomadradio]

Check R246 270 ohm 10 Watt. It's a wirewound, so it will probably check alive or dead, not in-between. If it has failed open, maybe it's the casualty of an overload. Maybe it's just 50-plus years old and died of old age.

If it's blown, next check CR2 and CR3. They may be surge damaged, if that was what popped R246.

Bear in mind that geriatric electrolytic filter capacitors can fail as a short, and then "heal" after they cool down. A test with low voltage from a meter will show okay. But when the full operating voltage is applied, they will break down again most of the time.

Not too many other things that can overload R246.

73

 

[Shockwave]

The way they labeled R46 as 270 ohms on this schematic makes it look like it is R246 at first glance. The diagnosis is 100% on target but the part number is R46 under closer examination.

 

[Shockwave]

I have a Executive that isn't showing any high voltage at the Filter Caps 100/100 500V , I disconnected the leads and the Caps test good. Looking at the schematic were should I start to look for my High Voltages?

Some voltages I tested.

Filter Caps both 0.0 Vdc

Converter Circuit:
Pin 4 13 Vac
Pin 5 7 Vac
Pin 6 O V

I.F. Unit
Pin 16 0 V
Pin 21 13 Vac
Pin 22 7 Vac

Audio Unit
Pin 33 & 35 0 V
Pin 36 12Vac
Pin 37 7Vac



http://www.cbtricks.com/radios/international_crystal/ctz_100c/graphics/ctz_100c_sch.pdf

I wish more problems were as well described and the needed reference material was supplied like this. Excellent job of presenting the problem in a way that made a quick and helpful response possible the first time.

Only thing I'll add is as Nomad says, the caps and diodes are old. Not a bad idea to replace all four part with the new resistor as preventive maintenance. Also pay attention for any smoke or excessive heat from the R46 when you power it up the first time. Having a Variac is nice for this.

There is a small chance that there could still be a problem down the line that overloaded this part. Because R45 would have almost twice the voltage drop across it, if it is still intact, that would isolate the problem to being diodes and or caps that caused R46 to fail.

 

[Crambone]

Thanks guys after digging around a bit more and looking at the addendum they have posted the power circuit was drafted wrong on the schematic. The good power circuit schematic is spot on.
Found the problem to be a cold loose solder joint on the Filter Cap ground. High voltage back and now onto looking for the rest of the snakes in the grass issues!

Once again thank you all for sharing your knowledge it’s always appreciated

 

[Shockwave]

Not for nothing but one open filter cap connection would not have caused the loss of high voltage. In fact, with two in the circuit the change here should have only caused an increase in AC ripple and 60 cycle hum. You may have some other intermittent but at least you have HV now. Good luck with the progress.

 

[Crambone]

That’s interesting, it is a dual cap and the ground goes to both so I’m not sure if that could have been the cause. I didn’t mention that I did remove the thermal trip also and bypassed. I forgot to add that part yesterday. I’m going to check all the voltages today as they do give a bunch in the manual. I will update with findings.