A Gemtune X-1 amp was shipped to me about two years ago with the rectifier tube broken, so it has yet to be plugged in. I would imagine it had the most common rectifier tube that would come with these. I lost the broken rectifier tube. My question is can a 5U4G (or any 5U4) from the 50's/60's be compatible in this amp. Or, would it be better to go with what it had originally.
The original tube was a type 5Z4P (I think). This is an indirectly heated filament/cathode type with a 5 volt 2 amp filament rating. An old 5U4G might work but has a 3 amp filament that the transformer might not like. (run hotter) And have a little higher output voltage drop. A closer match would be a 5V4 or 5V4G (same thing) or even a more modern 5AR4 (more expensive though). These each have the same indirect heater/cathode style and the same 5 volt 2 amp rating.
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I agree with HollowState, but I would stick with the original type. 5ZP4 is also what I found in a net search, confirming HollowState’s conclusion, BUT in a Russian made version, the 5ц4с (in Cyrillic). Do NOT use a western 5U4G unless you have verified that your power transformer can supply the required 3 amp heating current.
The confusion arrises due to the Russian 5ц4с that served as model for the functionally equivalent Chinese 5Z4P rectifier. There are a lot of Russian-made 5ц4с still a a available from internet sellers and that is what I would get to replace the lost 5Z4P. I like this “Cobra” version of this Ukrainian seller.
https://www.ebay.com/itm/1743514146...Sa8BgLrRxy&var=&widget_ver=artemis&media=COPY
The confusion arrises due to the Russian 5ц4с that served as model for the functionally equivalent Chinese 5Z4P rectifier. There are a lot of Russian-made 5ц4с still a a available from internet sellers and that is what I would get to replace the lost 5Z4P. I like this “Cobra” version of this Ukrainian seller.
https://www.ebay.com/itm/1743514146...Sa8BgLrRxy&var=&widget_ver=artemis&media=COPY
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Thank you for your quick responses and to my needs. You guys are awesome! I went ahead and purchased the one you sent me the link to.
Excellent! I have recently received tubes from Ukraine in good shipping time; I hope you do too.
Good luck and enjoy your Gemtune. -1.
Good luck and enjoy your Gemtune. -1.
One thing you should check is the value of the first cap in the power supply. I don't know about the Gemtune but many of the cheap Chinese amps use cap values that are waaay too high for the rectifiers that are used. It's a very common problem.
The data sheet for the stock rectifier specifies a maximum of 4uf. You can go a bit over this safely since this is a SE amp and the tube is not probably being run hard but I've seen some that use 150uf and even 300uf. This leads to rectifier failures and possibly other damage.
Another thing to check is heater voltages. Most all of the inexpensive Chinese amps use power transformers that are rated for 110v and when used with higher wall voltages the result is higher voltages throughout the amp. This is mostly an issue with the heaters and will shorten tube life considerably.
The data sheet for the stock rectifier specifies a maximum of 4uf. You can go a bit over this safely since this is a SE amp and the tube is not probably being run hard but I've seen some that use 150uf and even 300uf. This leads to rectifier failures and possibly other damage.
Another thing to check is heater voltages. Most all of the inexpensive Chinese amps use power transformers that are rated for 110v and when used with higher wall voltages the result is higher voltages throughout the amp. This is mostly an issue with the heaters and will shorten tube life considerably.
