Need 6U8 or 6U8 substitute info

[AF9J]

Hi Everybody,

Well, if it isn;t one thing, it's another!  The 6146B seems to be behaving itself in my Globe Scout 680.  BUT, wouldn't you know it, while I was firing up the Scout on Sunday morning, to do on-the-air tests with Steve, WD8DAS, I lost the the 6U8 driver!!  No Grid current at all!!  Ugh!!!  Steve told me, that 6U8s are kind of wimpy, and can't take much abuse.  To top it off, from what I've read, they're mainly receiver tubes!  Why on earth would WRL use a receiver tube for transmitting?!  It's akin to using sweep tubes!   OK......that's off my chest.  Now the question:

Should I go with a 6U8 substitute for a replacement, instead of a 6U8? If so, what (some of the substitutes seem to be even less common than the 6U8)?  I'd prefer something that's a little more robust.  Also (if possible), I'd like to not have to rip out half of the wiring to use a different driver tube.

73,
Ellen - AF9J

[KC1XF]

Hi Ellen,

The 6U8A was used in many color television receivers when they had tubes. It is a Medium MU Triode, also a Sharp Cutoff Pentode in one 9 pin configuration.

It can be replase with a 6GH8 or a 6EA8 which were also used in color tv's.

I think I have some of these over in the tube room, I will be glad to check tomorrow for you and if you need a couple I will be glad to send them to you.

Let me know if you need them.

73,

Fred
KC1XF

[AF9J]

Hi Fred,

Thanks.   Are the 6GH8 and 6EA8 a direct substitution, or would I need to do some rewiring?  Also, how much do you want for them?

73,
Ellen - AF9J

[Todd, KA1KAQ]

The 6U8/A is the one tube I could do without in my life. The KWM-2A uses a bunch of them, and they've never seemed to last worth a damn. This topic came up on the Collins reflector some time ago with one fellow insisting they were no different than any other tube. My experiences say otherwise. Put all new tubes in, run it now and then over a year or two, replace the 6U8s.

Drop either one of them in, Ellen. 6EA8 or 6GH8A.

[W1VD]

Ellen, Todd

As a bench tech at the local TV/Radio/2 way shop (circa 1970), we used to buy 6GH8As by the gross replacing more of them in TVs than any other tube type...by many orders of magnitude. Don't know if was poor application of the tube or if it was just a crappy tube.

At many hundred % markup guess it wasn't a bad thing...

 

[w3jn]

Another one in the KWM-2 that seems to go weak are the 6AZ8s.

RCA used a virtual forest of 6GH8s in their mid-60's color TVs.  They musta run 'em awfully hot as replacing 6GH8s was a well-known profit center amongst TV repairmen of the day.

[KC1XF]

Hi Ellen,

This may come up twice as I just sent it but didn't see it come up on the forum.

Yes Todd is correct the 6EA8 and 6GH8 are direct replacements for the 6U8A. Just plugged them in and you are set to go.

I have a 6EA8 which checked good on the tube checker. I will send it to you, please let me know if your address is correct on QRZ.

As was already said these were very popular tubes in the 60's and 70's tv's ate them up where they were used as color oscillators. TV shops used to buy them by the truck load. If I remember correctly there was better life using the 6EA8.

OK Ellen, let me know about the address and I will send it to you. BTW don't worry about the price. It was sitting around here collecting dust and it will be better if someone can use it.

73,

Fred
KC1XF

[Todd, KA1KAQ]

Jay & John - good point. I'd forgotten about the 6GH8A issues, not as bad as the 6U8A but close. They were used in a lot of 60s-70s 2 way gear and CBs as well. Wasn't unusual to see 3-4 of them in one set.

I don't recall seeing problems with the 6EA8, perhaps only because they aren't as prevalent?

[WQ9E]

Todd,

I think that the 6EA8 series may be a bit better but the SB-102 I had as my first rig after getting my general ticket seemed to go through a few of them.  I found out pretty quickly that the weaker ones would still function in some circuits so that saved on cost and downtime as I could swap them between sockets. As I recall the 102 has 3 or 4 6EA8's in it.  I did put a lot of hours on the SB-102 (mostly 15 and 20 CW), I have to get it hooked up again someday soon.

Rodger WQ9E

[The Slab Bacon]

The 6U8/A is the one tube I could do without in my life. The KWM-2A uses a bunch of them, and they've never seemed to last worth a damn. This topic came up on the Collins reflector some time ago with one fellow insisting they were no different than any other tube. My experiences say otherwise. Put all new tubes in, run it now and then over a year or two, replace the 6U8s.

Thats interesting, Todd. My kwummy 2 has had the same tubes in it since I got it many years ago. (mine is a govt surplus rig) I ran the snot out of it for a looooonnnggggg time including 4 or 5 field day expeditions and never had a tube failure. Not even the finals, running it much higher on voice peaks than Collins ever recommended. All of the tubes are still the same ones that were in it when I got it.

                                                      The Slab Bacon

[AF9J]

Hi Ellen,

This may come up twice as I just sent it but didn't see it come up on the forum.

Yes Todd is correct the 6EA8 and 6GH8 are direct replacements for the 6U8A. Just plugged them in and you are set to go.

I have a 6EA8 which checked good on the tube checker. I will send it to you, please let me know if your address is correct on QRZ.

As was already said these were very popular tubes in the 60's and 70's tv's ate them up where they were used as color oscillators. TV shops used to buy them by the truck load. If I remember correctly there was better life using the 6EA8.

OK Ellen, let me know about the address and I will send it to you. BTW don't worry about the price. It was sitting around here collecting dust and it will be better if someone can use it.

73,

Fred
KC1XF

Hi Fred,

Thanks!  That'll be great!  Yes my address in QRZ.com is good.  I tell you. This is great group! 

73,
Ellen - AF9J

[WU2D]

Yeah my NCX-3 used to eat 6U8's. It was always the triode section that would go because they used it to switch a 115VDC relay! One time the tube shorted and took out the relay. I found a 12V version of the relay and finally solid stated the whole circuit!

I think the 6U8 was the first triode pentode in one miniature tube -am I right?

Mike WU2D

[The Slab Bacon]

It is funny, everytime you pick up a box full of loose miniature tubes at a fester or swap meet there is always abundanza of 6U8s in there!! Kinda like 6SN7s were in boxes of loose octal toobz before the audiofools discovered them.

[N3DRB The Derb]

6u8's suck. I would rather have a DeForest audion in my rx, it would last longer. plus, if you hold the flame under it just right, it really increases the sensitivity. Cant do that with a 6u8. Teh are ghei. 

[W1RKW]

I remember 6EA8's being a PITA when I had my HW101.  I had have to go through a bunch of them to make the relay circuit work right.  I think I may have a bunch of them kicking around still.