Rca CTC-25 overview and help

[ZenithNut]

Originally Posted by Electronic M

Any of these should work for the boost diode. https://www.mouser.com/Semiconductor...r45Z1yopdfySGT May want to put 2 in series to ensure the replacement can take any possible voltage spike. Radio Shack used to sock a 2A 1.5KV part that I used to replace the boost on my CTC-15 but they ain't a thing anymore. Parts like diodes in sets of this vintage are probably over 3 generations obsolete so it is easier to look up the key specs and spec out a new one than find and trace forward all the missing links in the recommended successor line.

Any voltage of fuse is fine. The only spec that matters for fuses is the current. A you can take a .25A 125V fuse and put it in a device that wants a .25A 250V and vice versa and the device will work okay and the fuse will still blow at .25A current. You probably want a slow blow and not a fast acting fuse...The current averages ~200mA but spikes above 250mA for tiny fractions of each second. A fast act fuse is designed to catch that fractional spike and blow (creating lots of nuisance failure which you don't want) but the slow blow will average out the current and only blow when the average current reaches fault value.

Im gonna go with this guy for the boost diode.



https://www.mouser.com/ProductDetail...%252bUjA%3d%3d

Should work well right?

Also wanting to find a sub for 1n3195 heres the data sheet. There is a NOS 1n3195 on ebay for cheap. That is also an option.

https://www.datasheets360.com/part/d...1594065512865/

[Electronic M]

Originally Posted by ZenithNut

Im gonna go with this guy for the boost diode.



https://www.mouser.com/ProductDetail...%252bUjA%3d%3d

Should work well right?

Also wanting to find a sub for 1n3195 heres the data sheet. There is a NOS 1n3195 on ebay for cheap. That is also an option.

https://www.datasheets360.com/part/d...1594065512865/

First one you may want to put 2-3 in series to ensure against HV spikes/arcover causing it to short, but otherwise it seems fine.


The second diode looks like a common 1N4007 should be a sub for it.

In most tube circuits the important specs for the replacement diode to match or exceed are PIV (peak inverse voltage) and average forward current. The rest usually makes little difference.

[zeno]

One last thing is speed ( forgot what they called it ).
If you use a common 3A 1KV rectifier as a scan rectifier it will
blow within a few hrs because it overheats. Cant take the higher
freq. Same goes for in switching supplies.

IIRC boost diodes didnt test like a common diode ? I do remember
they rarely went bad.

73 Zeno
LFOD !

Originally Posted by Electronic M

First one you may want to put 2-3 in series to ensure against HV spikes/arcover causing it to short, but otherwise it seems fine.


The second diode looks like a common 1N4007 should be a sub for it.

In most tube circuits the important specs for the replacement diode to match or exceed are PIV (peak inverse voltage) and average forward current. The rest usually makes little difference.

[Electronic M]

Originally Posted by zeno

One last thing is speed ( forgot what they called it ).
If you use a common 3A 1KV rectifier as a scan rectifier it will
blow within a few hrs because it overheats. Cant take the higher
freq. Same goes for in switching supplies.

IIRC boost diodes didnt test like a common diode ? I do remember
they rarely went bad.

73 Zeno
LFOD !

With the virtual extinction of 60Hz linear power supplies most new rectifier diodes can handle at least horizontal rate switching. Even the humble 1n4007 is found in switch mode supplies these days. I've used many normal silicon rectifiers as boost and convergence doide replacements in tube sets had good results. The original boost and convergence diodes were selenium for fast switching...If they had the modern fast switching silicon diodes we had now back then they would have used them instead of seleniums.

Still it is not a.bad idea to convert switching time to seconds then take the inverse to get frequency and make sure that frequency is higher than that of the waveform applied.

[ZenithNut]

Originally Posted by Electronic M

First one you may want to put 2-3 in series to ensure against HV spikes/arcover causing it to short, but otherwise it seems fine.


The second diode looks like a common 1N4007 should be a sub for it.

In most tube circuits the important specs for the replacement diode to match or exceed are PIV (peak inverse voltage) and average forward current. The rest usually makes little difference.

I went to my local electronics shop and picked up a 1n4007 and a 1n5408 for the replacements