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Rectifier Tube Question

trobbins said:
Afaik the SP14 doesn't have a 6X5 heater-cathode related hum path, as the heater is a seperate winding with no other application.
The SP14 appears to use the 6X5 in a bridge rectifier, with ss diodes (which each have an added series resistor). If the 6X5 was the cause of some hum then that would indicate that one diode plate was significantly poor and that 60Hz ripple was significant.
But the lack of test info makes any technical conclusion a bit vague.
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Thanks for the info. I know the Sylvania rectifier tube causes hum, the GE doesn't. That's about all the troubleshooting skills I have :)
 
zackthedog said:
I've had two 6X5GT's fail in my old SP14 build, a Sylvania JAN just like geode's, and a NIB Brimar, which was quite expensive. :-( My new build is p-p and dispenses with the rectifier tube altogether.
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Egad...hoping against hope and fingers crossed.
 
init4fun said:
In the antique radio world, the 6X5 is notorious for taking out Zenith power transformers. Now in this case geode is running a pre amp with the 6X5 and not a radio complete with an audio output amp, so you should be fine with any of the later model 6X5 tubes, like the 6X5-GT you read about.

Here is a link to a discussion about the 6X5's appetite for old radio transformers and how to mitigate it ;

https://antiqueradios.com/forums//viewtopic.php?f=6&t=239368&start=0
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Thanks for the link, a good read. Transformer killer...oh my.
 
The 6X4 and 6X5 are prone to HK shorts unless the filament is powered by its own winding. This has been well-known since at least the '60s. The amplifiers in Akai M6-M7-M8 all utilize a separate winding for the 6X4, and my small SEP amps are configured the same way.

Jack
 
TriodeLuvr said:
The 6X4 and 6X5 are prone to HK shorts unless the filament is powered by its own winding. This has been well-known since at least the '60s. The amplifiers in Akai M6-M7-M8 all utilize a separate winding for the 6X4, and my small SEP amps are configured the same way.

Jack
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Was the problem fixed with the 6x5GT tube?
 
geode said:
Was the problem fixed with the 6x5GT tube?
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Don't know. I won't use any version of these unless the filament winding is separate and floating. There are other rectifiers in this power class that don't have a reputation for shorting (AFAIK). The 6V4 and 6BW4 come to mind.

Jack
 
gadget73 said:
except a pair of 1N4007 and a resistor
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That can over-voltage many of the caps and other components if the circuit wasn't designed for full B+ everywhere at power-on. I realize you know this, but it should probably be stated again to avoid misleading anyone about the benefits of SS rectifiers.

Jack
 
TriodeLuvr said:
That can over-voltage many of the caps and other components if the circuit wasn't designed for full B+ everywhere at power-on. I realize you know this, but it should probably be stated again to avoid misleading anyone about the benefits of SS rectifiers.

Jack
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Prolly what the resistor is for? :idea:

Anyhow, I've only replaced a few 6X5 rectified units with the Bendix 5852. AFAIK, they are still in those units (replace 15-20 years ago). One is a pretty fancy Audio Note DAC.

These 6X5 units tended to be in cheap US made 1960s clone-type guitar amps. And yeah, shorted out 6X5 leads to fried PTs. These rectifiers were prolly originally made for cheap car radios and not hi-fi or guitar amps.

If you want to keep the circuit, the 5852 does work. But, it draws more heater current than a typical 6X5GT So, you are better off with a separate 6.3VAC transformer --- or converting the PT to have a 5VAC tap and use a 5Y3GT rectifier.

I like GE black plate 5Y3GT. Bendix 6106 for a long, long, long lasting slow warm-up rectifier.
 
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resistor will handle full load voltage but it will come up immediately and with no load some parts may see higher voltages than they are rated for. Nothing that can't be dealt with but certainly it does want to be looked at.
 
TriodeLuvr said:
Don't know. I won't use any version of these unless the filament winding is separate and floating. There are other rectifiers in this power class that don't have a reputation for shorting (AFAIK). The 6V4 and 6BW4 come to mind.

Jack
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Mine hasn't Nova'd, yet. Fingers crossed. There doesn't seem to be a drop in replacement tube for it.
 
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