When I switch on the 100kHz calibrator in my TR-4, I get a constant tone regardless of the frequency of the PTO.  It's rather high-pitched, perhaps 4 kHz or 5 kHz in frequency.  If I recall correctly, it seems more prevalent in one sideband setting or the other (not sure which at the moment).

I presume this is not normal, correct?  If it isn't, any suggestions as to what might be the problem?  I know the crystal and tube are pretty close to the RF TUNE capacitor (which is in a metal cover) and am wondering if that may be where it's getting picked up but that might not have anything to do with it.  I'm hoping someone else has seen this and might know where to look.

Thanks,
Barry - N4BUQ

Sorry guys.? I meant to send that directly to Gary.

Barry - N4BUQ

Hi Gary,

Have those tubes shipped?? The tracking says the shipping label was created on the 8th but still just says USPS is awaiting the item so thought I'd ask.

Thanks,

Barry - N4BUQ

---

From: "Barry" <n4buq@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Wednesday, May 7, 2025 11:55:19 AM
Subject: Re: [DRAKE-RADIO] 6EA8 - Brand Recommendations?

Hi Gary,

Well, I struck out.? I have a very nice-looking Sylvania 6EA8 empty box but that's all I could find.? Please let me know how you'd like to handle this.

Thanks again,

Barry - N4BUQ

Hi Gary,

I'd like to get one of the Sylvania 6U8s and one of the RCA 6EA8s.? I'm hoping that will help the TR-4 just a bit.? I'm still unsure why only one of the three 6EA8s I have work properly in the V1 position and hopefully a new one will but who really knows why these others aren't working there.

With that said, can we hold off a couple of days on this?? I have a box of miniature tubes that I haven't gone through and it's possible there are some candidates in there that I'd like to try first.? I'll get back with you after that if that's okay.

Thanks again,

Barry - N4BUQ

---

From: "Gary Follett via groups.io" <xntrick1948@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Tuesday, May 6, 2025 2:51:52 PM
Subject: Re: [DRAKE-RADIO] 6EA8 - Brand Recommendations?

Hi Barry.

I have a mixed lot. Most are new in boxes.?

I have two Sylvania 6U8, a Sylvania 6GH8 and ?that are new but not in boxes and one Sylvania 6U8 new in box.

I have two International (Japanese) new in boxes.

I have a JAN (ECG/Sylvania) 6U8 new in box.

I have a new logo RCA 6EA8 new in box.I have an old logo RCA 6EA8 new in box.

I have a GE 6GH8 new in box.

Take your pick, $5 each plus $4 to mail them.

Gary

On May 6, 2025, at 8:26?AM, n4buq <n4buq@...> wrote:

Do you have one or two you'd like to sell?

Thanks,

Barry - N4BUQ

I think I have about 25 new old stock 6EA8 variations…

Gary

W0DVN

On May 5, 2025, at 1:31?PM, n4buq <n4buq@...> wrote:

As a test, I removed V2 from my 2-B. ?That's supposed to be a 6U8 but apparently someone subbed a 6EA8 in that position (a Sylvania). ?I say "apparently", because the label is partially damaged but I'm pretty sure the last two letters are "A8" so pretty sure it's a 6EA8.

I tried that in the V1 position of my TR-4 but it also produces very low oscillator voltages (on the order of less than 1 volt) so that leaves me with only one 6EA8 that will work well in that spot. ?I'm guessing some other property of the tubes is causing this.

Since the triode section of V3 is a cathode follower that feeds the pentode mixer section in the TR-4, I'm not sure how much a weak triode in that location will affect overall performance but I suspect it does.

I have several random spare 6V miniature tubes - mostly from what I think was surplus from a TV repair business - but I don't think I have any 6EA8s or 6U8s so I may take my chances getting another one that supposedly tests strong (as that's about all I'd have to go on).

Thanks,
Barry - N4BUQ

I presume a 6U8 is one of he variations, correct? ?I see where it appears to be
a good sub but not sure if there are any caveats using them in these circuits.
I see where Drake stayed with 6EA8 in V1 and V3 for the entire TR-4 run.

Thanks!
Barry - N4BUQ

All 6EA8 and variations were terrible - great money makers for me when I was
fixing TV sets in university. Too much stuff in a tiny envelope...

RCA made the most of them. They were no better nor worse than any of the others.
They all suffered from inter electrode leakage and shorts.

Sylvania’s were pretty good. If I had to stay away from one, I’d skip the GE’s.

Surprisingly, Lindall (Japanese) were pretty good, so good that Raytheon sold
them under their name.

Gary

W0DVN

On May 4, 2025, at 7:55?PM, n4buq <n4buq@...> wrote:

Still trying to troubleshoot my TR-4. ?I started checking the tube voltages and
found a very weak 6EA8. ?I was getting about -1.7v at the test point so I tried
swapping V1 and V3. ?That resulted in the test point dropping to about -0.5v.
The Hickok 752A also showed the triode being only slightly above the minimum
for that tube so I'm thinking of getting a pair where both halves of both tubes
will be strong.

Any recommendations on brands? ?Mine are RCA and I suspect that should be a good
brand for them but I also figure that brand may not be as critical as for, say,
the PA tubes.

Thanks,
Barry - N4BUQ

Hi Gary,

Have those tubes shipped?? The tracking says the shipping label was created on the 8th but still just says USPS is awaiting the item so thought I'd ask.

Thanks,

Barry - N4BUQ

---

From: "Barry" <n4buq@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Wednesday, May 7, 2025 11:55:19 AM
Subject: Re: [DRAKE-RADIO] 6EA8 - Brand Recommendations?

Hi Gary,

Well, I struck out.? I have a very nice-looking Sylvania 6EA8 empty box but that's all I could find.? Please let me know how you'd like to handle this.

Thanks again,

Barry - N4BUQ

Hi Gary,

I'd like to get one of the Sylvania 6U8s and one of the RCA 6EA8s.? I'm hoping that will help the TR-4 just a bit.? I'm still unsure why only one of the three 6EA8s I have work properly in the V1 position and hopefully a new one will but who really knows why these others aren't working there.

With that said, can we hold off a couple of days on this?? I have a box of miniature tubes that I haven't gone through and it's possible there are some candidates in there that I'd like to try first.? I'll get back with you after that if that's okay.

Thanks again,

Barry - N4BUQ

---

From: "Gary Follett via groups.io" <xntrick1948@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Tuesday, May 6, 2025 2:51:52 PM
Subject: Re: [DRAKE-RADIO] 6EA8 - Brand Recommendations?

Hi Barry.

I have a mixed lot. Most are new in boxes.?

I have two Sylvania 6U8, a Sylvania 6GH8 and ?that are new but not in boxes and one Sylvania 6U8 new in box.

I have two International (Japanese) new in boxes.

I have a JAN (ECG/Sylvania) 6U8 new in box.

I have a new logo RCA 6EA8 new in box.I have an old logo RCA 6EA8 new in box.

I have a GE 6GH8 new in box.

Take your pick, $5 each plus $4 to mail them.

Gary

On May 6, 2025, at 8:26?AM, n4buq <n4buq@...> wrote:

Do you have one or two you'd like to sell?

Thanks,

Barry - N4BUQ

I think I have about 25 new old stock 6EA8 variations…

Gary

W0DVN

On May 5, 2025, at 1:31?PM, n4buq <n4buq@...> wrote:

As a test, I removed V2 from my 2-B. ?That's supposed to be a 6U8 but apparently someone subbed a 6EA8 in that position (a Sylvania). ?I say "apparently", because the label is partially damaged but I'm pretty sure the last two letters are "A8" so pretty sure it's a 6EA8.

I tried that in the V1 position of my TR-4 but it also produces very low oscillator voltages (on the order of less than 1 volt) so that leaves me with only one 6EA8 that will work well in that spot. ?I'm guessing some other property of the tubes is causing this.

Since the triode section of V3 is a cathode follower that feeds the pentode mixer section in the TR-4, I'm not sure how much a weak triode in that location will affect overall performance but I suspect it does.

I have several random spare 6V miniature tubes - mostly from what I think was surplus from a TV repair business - but I don't think I have any 6EA8s or 6U8s so I may take my chances getting another one that supposedly tests strong (as that's about all I'd have to go on).

Thanks,
Barry - N4BUQ

I presume a 6U8 is one of he variations, correct? ?I see where it appears to be
a good sub but not sure if there are any caveats using them in these circuits.
I see where Drake stayed with 6EA8 in V1 and V3 for the entire TR-4 run.

Thanks!
Barry - N4BUQ

All 6EA8 and variations were terrible - great money makers for me when I was
fixing TV sets in university. Too much stuff in a tiny envelope...

RCA made the most of them. They were no better nor worse than any of the others.
They all suffered from inter electrode leakage and shorts.

Sylvania’s were pretty good. If I had to stay away from one, I’d skip the GE’s.

Surprisingly, Lindall (Japanese) were pretty good, so good that Raytheon sold
them under their name.

Gary

W0DVN

On May 4, 2025, at 7:55?PM, n4buq <n4buq@...> wrote:

Still trying to troubleshoot my TR-4. ?I started checking the tube voltages and
found a very weak 6EA8. ?I was getting about -1.7v at the test point so I tried
swapping V1 and V3. ?That resulted in the test point dropping to about -0.5v.
The Hickok 752A also showed the triode being only slightly above the minimum
for that tube so I'm thinking of getting a pair where both halves of both tubes
will be strong.

Any recommendations on brands? ?Mine are RCA and I suspect that should be a good
brand for them but I also figure that brand may not be as critical as for, say,
the PA tubes.

Thanks,
Barry - N4BUQ

From: "Barry" <n4buq@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Wednesday, May 7, 2025 11:55:19 AM
Subject: Re: [DRAKE-RADIO] 6EA8 - Brand Recommendations?

Hi Frank,

?

Really 500Kc?? Could it be 500c? (500Hz nowadays)?

?

500-800Hz is about the normal C line offset.

You should use LSB on the R-4 for CW.. could you be using USB?

?

73,

Gary

WB6OGD

Hi Frank,

?

Really 500Kc?? Could it be 500c? (500Hz nowadays)?

?

500-800Hz is about the normal C line offset.

You should use LSB on the R-4 for CW.. could you be using USB?

?

73,

Gary

WB6OGD