>
>----- Forwarded Message ----
>From: Mark Nace <[email protected]>
>To: Walker <[email protected]>
>Cc: mark nace <[email protected]>
>Sent: Saturday, September 5, 2009 10:37:15 AM
>Subject: Re: [Drakelist] Which tubes are the right tubes
>
>
>Phil,
>You are feeling the same pain as I have over the years on the TR-4
>documentation. I have two original manuals with the associated schematics. I
>can help a little, so here goes:
>
>1. The early Drake TR-4's were sort of transitional from the TR-3. TR-3's
>used to have 12BA6's for both X-mit IF amp (V15) and Receive (V11 and V12) IF
>amps .
>2. In the TR-4's, they started going to 6BZ6's in the first receive IF amp
>(V11), but kept 12BA6 as the second receive IF (V12). In both schematic
>versions I have, the 1st received IF V11 was just whited out by Drake, and a
>"6" is penciled in. Same with the "Z". so, 12BA6 went to 6BZ6.
>3. Also in the TR-3's, the crystal calibrator (V5) used to be a 12BA6. In
>the TR-4's, they switched to the 6BZ6 in the voltage and resistor charts, BUT,
>the schematic for serial numbers 30,500 and later show a 6BA6 as the crystal
>calibrator, whereas schematic for serial numbers 28,500 and later showed a
>6BZ6 as V5.
>4. You may have an old version of the manual, and a newer version of the
>schematic. The reason I think so, is that the 12BZ6 was used as the 1st rec.
>IF (V11) in very early TR-4's. Even in these later manuals, if you look at
>the pictures, the use serial number 16050, which was probably the first TR-4
>prototype they started selling. Moreover, if you look closely at the
>top-chassis picture, you can just BARELY see that V11 was labeled as 12BZ6. I
>think they changed it out over the course of production. Also, they show
>12BA6 in this picture as the crystal cal. tube. So, the pictures are
>misleading for later models, even though the voltage and resistance charts, as
>well as schematics were updated. That's why the charts in your manual are why
>they list 12BA6 and 12BZ6 as V5 and V11 respectively.
>5. V4 in theTR-3 used to be a 6HS6 (transmit mixer), but later they switched
>to the 6EJ7 as the mixer, and it also shows up in the top-chassis picture as
>6EJ7 !
>6. Even in the latest version of the manual I have, 6HS6 is still listed in
>the block diagram, but the charts show the 6EJ7. Guess they forgot to change
>that in the block diagram.
>
>Yes, there WERE changeovers, as you say, and some glaring inconsistencies
>through the years. I would trust the chassis lettering, and try to get a
>later version of the manual.
>
>Hope this is as clear as mud,and good luck. We can keep the dialog going for
>sure.
>
>73,
>Mark
>N5KAE
>
>>
>>From: Walker <[email protected]>
>>To: [email protected]
>>Sent: Saturday, September 5, 2009 7:47:46 AM
>>Subject: [Drakelist] Which tubes are the right tubes
>>
>>I have a TR-4, 1968 manufacture date, serial number 28124. It has worked well
>>for years, with the last few being dormant as my vertical took a hit a few
>>winters ago with icing. I've replaced the vertical, and I'm trying to re-tube
>>the unit. Here is where the confusion arises:
>>
>>The chassis lettering and schematic for tubes V4, V5, V11 and both agree and
>>are respectively: 6EJ7, 6BA6, 6BZ6.
>>
>>Note: the schematic has V5 and V11 with a hand lettered "6" in front of 6BA6
>>and 6BZ6 versus all other tubes which have stencil guided lettering.
>>
>>The Manual's Voltage Reference chart and Tube List for V4, V5 and V11 are:
>>6EJ7, 12BA6, 12BZ6
>>
>>The Manual's Block Diagram shows V4 as 6HS6
>>
>>I'm not sure what's supposed to be right, though I have a tendency to believe
>>the chassis lettering and schematic. The manual is internally inconsistent,
>>and doesn't agree with the physical hardware or schematic. I probably can
>>take out V5 and V11 and measure the filament voltage present to see if it
>>really is set up for a 6 or 12 volt tube in those sockets.
>>
>>I found some correspondence between the original owner, whom I purchased the
>>unit from, and the factory regarding a technical problem. The factory rep
>>wasn't sure in solving a problem whether the former owner needed a 6BZ6 or a
>>12BZ6 so he sent him one of each. Apparently the factory didn't know either!
>>
>>Was there some changeover for different serial number ranges, between various
>>tube types or what, and what is the best way to tell which tubes really
>>belong in the circuits?
>>
>>Thanks for pointing me toward a resource, if you know one, to help get some
>>answers.
>>
>>Phil WA2CLX
>>
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
