Leak TL12+ smoothing capacitors.

[mickg]

I want to replace the large PSU smoothing capacitor on my leak TL12+.
I would like to fit a JJ dual can electrolytic as they seem to be of a similar construction to the original C13 and C14 currently fitted.
The current capacitor is 100 + 60 microfarads but the JJ comes as 100 + 100 microfarads @500V.
So my question is would this be a suitable replacement even though one of the values is almost twice the required value ?.
Thanks.

 

[indianajo]

When you go over on B+ capacitance, you have to make sure you don't go over the surge current rating on the rectifier tube. One way to do this is mount a resistor between the tube cathodes and the oversize capacitor. I used a 47 ohm 5 w resistor mounted on a solder type terminal strip under the deck in my amp (not a leak). The voltage drop is not significant since wall socket voltage is so much higher now than it was in 1955. A 3 W resistor was too small on my 5AR4 and went transparent under the heat. A lower current rectifier tube like a 6x4 or 5Y4 may be fine with a 3 W resistor.
You could also instead put two resistors between the transformer winding and the rectifier tube plates, which also helps protect the transformer against rectifier tube shortout. A 3 W resistor in each place might burn out (good) if the rectifier tube shorts. This requires moving around the transformer leads to a terminal strip, which could be problematic if you are not a smooth solder iron operator. I didn't do that.
I buy my terminal strips at tubesandmore.com, triodeelectronic.com, or electronicsurplus.com. There aren't any at the major parts houses, and I don't know of a source in Europe. Don't forget a small roll of 600 v rated wire on the order, you may need to extend the existing wiring a little with the extra part. There is a China retail source of solder terminal strips, if you are in Asia.

 

[Merlinb]

100uF is pushing it for a GZ34, unless you add some resistance as indianajo mentioned. Suggest you look for a more suitable cap replacement.

 

[mickg]

smoothing capacitors

thanks for the replies which have been helpful but I need to get this right as I don't want to destroy my amplifier.
After a little more investigation and research I have noticed on some schematic drawings for the leak tl12+ that the smoothing capacitors C13 and C14 are quoted as 32 microfarads each whereas on other drawings they are C13, 100microfarads and C14 60microfarads (which are fitted to my amp).
So could I assume that fitting a JJ 32 + 32 would be o.k. or even a 50 + 50.
thanks.
mickg.

 

[indianajo]

If you have a GZ34 (5AR4) 30 +20 is fine in my ST70, with a choke between rectifier tube and capacitor. My hammond H100 organ has 50 on each 5AR4, but it has a "40 ohm" choke between each rectifier tube and the first capacitor. Since the wall socket voltage is so high these days, and the quality of rectifier tubes is below 1960, I would put either a choke or resistance in as I said. And have been doing in all the H100 organs that use the 5AR4. I have had a couple of Russian made 5AR4 's from triodeelectronics.com in one of the organs, since 2011. So far so good, with the 47 ohm resistance plus the stock choke. I'm saving the cherry Hammond vacuum rectifiers for a rainy day.

 

[Triodethom]

duncan amps PSDII that free will help you with sizing try it. You can set up what leak used then play with adding chokes or resistors and more cap.