Just inherited a Heathkit lowboy/chairside radio phono (mono) console, w/Garrard RC88/4 changer. AM tuner BC-1A; FM tuner FM-3A; Preamp WA-P2; Pwr amp W-5M; Acoustic Craft 12" bass reflex enclosure. Have schematics. Tuners mounted to a tilt-out, pre amp resides vertically along side the changer under hinged lid, pwr amp under tuners behind tilt-out. Web specs pretty good, but ANYTHING REMARKABLE ABOUT THIS SET? Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems. Except for the cig smoke, rat droppings and severe cabinet damage, all components were there.

marv

:Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems.:
:marv
:
Marv, you may be thinking of 6X5s. They were prone to shorts between the heater and cathode, which could blow out the power xfmr. I'm unaware of a similar problem with 6X4s.

Thanks Doug.
Yea, thats the post I was referring to. At least I got 2 digits correct. Only partial dementia, I think, but can't remember lol.

marv

::Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems.:
::marv
::
:Marv, you may be thinking of 6X5s. They were prone to shorts between the heater and cathode, which could blow out the power xfmr. I'm unaware of a similar problem with 6X4s.
:

More:

A 6X4 and a 6X5, performance-wise, are the same tube. Both have directly heated cathodes - and if the internal H-K insulation breaks down, the cathode (K) will be shorted to the heater (H). And the xfmr goes Zap! (Zenith had to make good on a bunch of pre-war warranty claims caused by 6X5 H-K shorts. More info here: http://enginova.com/Zenith_10S464.htm )

6X5s are octals, and came out pre-war, while the 6X4 is a 7-pin miniature. I haven't heard of failures of the 6X4, and I assume they are OK. Even many 6X5s work fine and haven't failed.

I presume you have a hi-voltage cap/resistor checker? You could use it to measure the resistance between the cathode and heater of your 6X4s. I don't know what the ohm specs would be, but you could calculate the H-K voltage drop once you know the insulation resistance. You'd want that voltage drop to be essentially equal to the total B+ across the rectifier tube, i.e., little or no leakage.

You could also impress a known B+ voltage across the H-K insulation, in series with a fixed resistor, and measure the voltage across the fixed resistor to compute the tube's H-K resistance. I have a supply of good 6X5s, and might perform a little experimental testing.

'course, one problem might be that an H-K short could happen all at once on a perfectly good tube?

:More:
:
:A 6X4 and a 6X5, performance-wise, are the same tube. Both have directly heated cathodes - and if the internal H-K insulation breaks down, the cathode (K) will be shorted to the heater (H). And the xfmr goes Zap! (Zenith had to make good on a bunch of pre-war warranty claims caused by 6X5 H-K shorts. More info here: http://enginova.com/Zenith_10S464.htm )
:
:6X5s are octals, and came out pre-war, while the 6X4 is a 7-pin miniature. I haven't heard of failures of the 6X4, and I assume they are OK. Even many 6X5s work fine and haven't failed.
:
:I presume you have a hi-voltage cap/resistor checker? You could use it to measure the resistance between the cathode and heater of your 6X4s. I don't know what the ohm specs would be, but you could calculate the H-K voltage drop once you know the insulation resistance. You'd want that voltage drop to be essentially equal to the total B+ across the rectifier tube, i.e., little or no leakage.
:
:You could also impress a known B+ voltage across the H-K insulation, in series with a fixed resistor, and measure the voltage across the fixed resistor to compute the tube's H-K resistance. I have a supply of good 6X5s, and might perform a little experimental testing.
:
:'course, one problem might be that an H-K short could happen all at once on a perfectly good tube?
:
:

:
: I have used a 0Z4 cold cathode tube to replace a 6X5 application. B+ was fine.
:
We were talking about a 6X4 here. But anyway, a 0Z4 has a different pin-out than a 6X5. Hard for me to understand how a 0Z4 could replace a 6X5 without much rewiring.

I take that back. I can see how an 0Z4 could work. Some of the operating characteristics differ from a 6X5, though - but evidently not significantly so.

Since an 0Z4 is an octal, it couldn't replace a 6X4, of course.

Thanks for all the input. I'm anxious to get into this Heathkit stuff, but it'll have to wait while I clear out my other 3 projects. The tuners and preamp are in bad shape with front panels needing complete restoration. Dirt, grime, rust, pitting, and dial glasses are almost unreadable. Haven't even opened any of them to see whats inside, other than mouse droppings and grime. Looking at schematic, FM front end, appears to be just a broadband circuit, with very little selectivity at the input. Maybe in the 50's, so few FM stations were on the air, you were lucky to find one, and didn't really need a very selective front end.

marv

:Just inherited a Heathkit lowboy/chairside radio phono (mono) console, w/Garrard RC88/4 changer. AM tuner BC-1A; FM tuner FM-3A; Preamp WA-P2; Pwr amp W-5M; Acoustic Craft 12" bass reflex enclosure. Have schematics. Tuners mounted to a tilt-out, pre amp resides vertically along side the changer under hinged lid, pwr amp under tuners behind tilt-out. Web specs pretty good, but ANYTHING REMARKABLE ABOUT THIS SET? Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems. Except for the cig smoke, rat droppings and severe cabinet damage, all components were there.
:
:marv
:

Hi Marv,

I recently restored a WA-P2 and W-5M. I found that ALL the capacitors were leaky to some extent with some of the electrolytics shorted and beyond reforming. After restoration you will find that the W-5M is an excellent amplifier, worthy of its reputation.

Meade

:Thanks for all the input. I'm anxious to get into this Heathkit stuff, but it'll have to wait while I clear out my other 3 projects. The tuners and preamp are in bad shape with front panels needing complete restoration. Dirt, grime, rust, pitting, and dial glasses are almost unreadable. Haven't even opened any of them to see whats inside, other than mouse droppings and grime. Looking at schematic, FM front end, appears to be just a broadband circuit, with very little selectivity at the input. Maybe in the 50's, so few FM stations were on the air, you were lucky to find one, and didn't really need a very selective front end.
:
:marv
:
::Just inherited a Heathkit lowboy/chairside radio phono (mono) console, w/Garrard RC88/4 changer. AM tuner BC-1A; FM tuner FM-3A; Preamp WA-P2; Pwr amp W-5M; Acoustic Craft 12" bass reflex enclosure. Have schematics. Tuners mounted to a tilt-out, pre amp resides vertically along side the changer under hinged lid, pwr amp under tuners behind tilt-out. Web specs pretty good, but ANYTHING REMARKABLE ABOUT THIS SET? Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems. Except for the cig smoke, rat droppings and severe cabinet damage, all components were there.
::
::marv
::
:

MAG,
Thanks for the input. Just hope the FM tuner lives up to Heathkit's reputation. I'm trying to remember, but seems this front end circuit is called cascode. A std common cathode followed by a common grid (grounded grid) stage. Very stable gain stage(s), but with lower input impedance for antenna matching, but no first stage tuning/selectivity.

marv

:Hi Marv,
:
:I recently restored a WA-P2 and W-5M. I found that ALL the capacitors were leaky to some extent with some of the electrolytics shorted and beyond reforming. After restoration you will find that the W-5M is an excellent amplifier, worthy of its reputation.
:
:Meade
:
:
::Thanks for all the input. I'm anxious to get into this Heathkit stuff, but it'll have to wait while I clear out my other 3 projects. The tuners and preamp are in bad shape with front panels needing complete restoration. Dirt, grime, rust, pitting, and dial glasses are almost unreadable. Haven't even opened any of them to see whats inside, other than mouse droppings and grime. Looking at schematic, FM front end, appears to be just a broadband circuit, with very little selectivity at the input. Maybe in the 50's, so few FM stations were on the air, you were lucky to find one, and didn't really need a very selective front end.
::
::marv
::
:::Just inherited a Heathkit lowboy/chairside radio phono (mono) console, w/Garrard RC88/4 changer. AM tuner BC-1A; FM tuner FM-3A; Preamp WA-P2; Pwr amp W-5M; Acoustic Craft 12" bass reflex enclosure. Have schematics. Tuners mounted to a tilt-out, pre amp resides vertically along side the changer under hinged lid, pwr amp under tuners behind tilt-out. Web specs pretty good, but ANYTHING REMARKABLE ABOUT THIS SET? Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems. Except for the cig smoke, rat droppings and severe cabinet damage, all components were there.
:::
:::marv
:::
::
:

Forum,
Are there any codes or ID's or standard colors to reproduce the Heathkit gold used on these sets? It almost appears to be a metallic, but then again a very muted metallic. Or maybe a brass tone metallic vs gold. May be their secret?

marv

:MAG,
:Thanks for the input. Just hope the FM tuner lives up to Heathkit's reputation. I'm trying to remember, but seems this front end circuit is called cascode. A std common cathode followed by a common grid (grounded grid) stage. Very stable gain stage(s), but with lower input impedance for antenna matching, but no first stage tuning/selectivity.
:
:marv
:
::Hi Marv,
::
::I recently restored a WA-P2 and W-5M. I found that ALL the capacitors were leaky to some extent with some of the electrolytics shorted and beyond reforming. After restoration you will find that the W-5M is an excellent amplifier, worthy of its reputation.
::
::Meade
::
::
:::Thanks for all the input. I'm anxious to get into this Heathkit stuff, but it'll have to wait while I clear out my other 3 projects. The tuners and preamp are in bad shape with front panels needing complete restoration. Dirt, grime, rust, pitting, and dial glasses are almost unreadable. Haven't even opened any of them to see whats inside, other than mouse droppings and grime. Looking at schematic, FM front end, appears to be just a broadband circuit, with very little selectivity at the input. Maybe in the 50's, so few FM stations were on the air, you were lucky to find one, and didn't really need a very selective front end.
:::
:::marv
:::
::::Just inherited a Heathkit lowboy/chairside radio phono (mono) console, w/Garrard RC88/4 changer. AM tuner BC-1A; FM tuner FM-3A; Preamp WA-P2; Pwr amp W-5M; Acoustic Craft 12" bass reflex enclosure. Have schematics. Tuners mounted to a tilt-out, pre amp resides vertically along side the changer under hinged lid, pwr amp under tuners behind tilt-out. Web specs pretty good, but ANYTHING REMARKABLE ABOUT THIS SET? Noted 6X4 rectifiers in the tuners, and seem to remember a past post regarding their problems. Except for the cig smoke, rat droppings and severe cabinet damage, all components were there.
::::
::::marv
::::
:::
::
: