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 Post subject: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Mon 26, 2018 3:16 pm 
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Joined: Nov Sat 22, 2008 5:14 am
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Location: Framingham, Ma
hi friends,

i have an early 50s danelectro guitar amp (2x6L6s / 12" speaker)

in it's tube lineup there is a 6Y6 (NOT utilized as output tube) i realize these were more popular way back ; )
i'm not sure it's function but it is getting very microphonic.
is it ok to sub a healthy 6V6 in 6Y6s place?

thank you all,
mike


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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Mon 26, 2018 3:45 pm 
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mikeC wrote:
is it ok to sub a healthy 6V6 in 6Y6s place?
I'm speculating that the 6Y6 is a driver and perhaps phase inverter for the 6L6s.

Substituting a 6V6 for a 6Y6 seems entirely practical and at the same time gets rid of a bunch of filament supply drain (1.25 A for a 6Y6 versus .45 A for a 6V6). It certainly won't hurt anything to try it. The 6V6 is capable of operating with much higher plate voltage than a 6Y6 also. The bias might be a little off, but probably within reason.

So, the tube will operate somewhat differently, but should be satisfactory as a driver for the 6L6s. I don't see any harm in trying it.

You would generally not want to substitute in the OTHER direction (6V6 to 6Y6) because of that extra filament current drain on a power transformer (extra 0.8 A) and the lower plate voltage design of the 6Y6 (you can run higher voltages but have to really turn up the negative bias to prevent over current).

Curtis Eickerman

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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Mon 26, 2018 4:47 pm 
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Joined: Nov Sat 22, 2008 5:14 am
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Location: Framingham, Ma
thanks for such a thoughtful reply, curtis
let's see how it <sounds>
will try and report back,
mike


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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 3:09 am 
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I just looked at 7 or 8 schematics but saw none that use a 6Y6 for a driver or phase inverter, but that doesn't say it wasn't done, such as if they were overstocked with old inventory.

Does the amp have tremolo or a reverb loop? Could be for that.
Sometimes people will plug any old tube into a socket. I have a 6 tube radio here that came to me with 4 random incorrect tubes plugged into it.

http://el34world.com/charts/Schematics/ ... matics.htm

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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 3:30 pm 
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Location: South Jersey East of Philly
It would be helpful to post a model number and/or pic of the amp and chassis.


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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 5:48 pm 
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westcoastjohn wrote:
I just looked at 7 or 8 schematics but saw none that use a 6Y6 for a driver or phase inverter, but that doesn't say it wasn't done, such as if they were overstocked with old inventory.
Yes, the common theme on their amplifiers seems to be 6SN7 or 6FQ7 drivers for 6L6 output tubes and using a separate smaller phase inverter.

Without a model number and/or schematic it's a big guessing game.

Curtis Eickerman

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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 7:24 pm 
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Joined: Nov Sat 22, 2008 5:14 am
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Location: Framingham, Ma
fellas,

forgive me being so incommunicado ... tube in question was NOT a 6y6 but a 6j5. amp in question is a Maestro. dano circuits, even within same models, could change frequently. tube in question had been wiped clean and i used a pic i found online to identify (incorrectly) the tube.

so in effect i subbed a 6v6 where a 6j5 was needed. it worked but w/ a loss of high end. i soon realized tube was in fact a 6j5 yada yada yada. i'm currently waiting on a nos sylvania 6j5.

whew ; )

tube lineup is 5y3 2x6l6 2x12sj7 6sn7gta and 6j5

thank you all! AR forum is easily one of the best on the web.

best regards,
mike


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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 8:22 pm 
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mikeC wrote:
so in effect i subbed a 6v6 where a 6j5 was needed. it worked but w/ a loss of high end.
Kind of got lucky on that one. All the pins would have been the same except the screen grid of the 6V6 was not connected and therefore lousy performance.
mikeC wrote:
tube lineup is 5y3 2x6l6 2x12sj7 6sn7gta and 6j5
Sure enough, a 6SN7 driving the 6L6s.

Best of luck,

Curtis Eickerman

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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Feb Wed 28, 2018 8:51 pm 
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Joined: Nov Sat 22, 2008 5:14 am
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Location: Framingham, Ma
thank you, curtis, et al

what do the 12sj7s do? amp does have vibrato.
besides output and rectifier swaps i wonder where tone could benefit from trying different tubes?

best,
mike


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 Post subject: Re: Substitute 6V6 in place of 6Y6 ???
PostPosted: Mar Fri 02, 2018 3:39 am 
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Not Curtis, but can answer this one. :lol:
A beam power tube, such as a 6V6 is used only in the final output as a rule. That was why we questioned it as a driver.

Two 12SJ7 tubes in a guitar amp would be preamps.
Sometimes the effect, such as vibrato, will be on a loop that can be switched in or out of the normal circuit. If the effect causes some loss to the signal, such as a reverb can with springs, they will wire a unused triode, or several, to amplify that signal going back into the circuit.

To learn more about the 12SJ7, Google it and find a page of tube characteristics or data. I like the radio museum pages because I'm used to them, but better pinouts can be found in Images or on other pages.

It is a single stage tube, a pentode. You could figure out the wiring to the tube sockets fairly easily if there is no schematic. Probably the two 12SJ7's coupled to the 6SN7 with capacitors. Then the 6J5 might be on a vibrato loop. Maybe each 12SJ7 is wired as a separate input.

The schematic above for the "special" comes close, but the 6J5 is subbed with a 3rd 6SJ7, I think.
(Your 12SJ7 uses a 12 volt heater, otherwise same thing, wired the same.)

If* you were to change one of those sockets to a 9-pin type, you could install a 12AX7 preamp tube, which gives you two stages of gain in one tube. The wiring would be copied from a late 50's Fender circuit.
*Not recommended on a collectible, but you could build another amp like this one.

For the best tone quality, your first preamp tube should be a good one, a strong 12SJ7, as it amplifies the signal when it is the cleanest.
The way the Danelectro 'Special' is wired, the signal has to travel past a tone and a volume control before that first stage. If you bypassed those two pots and connected the 68K resistor to a new cap on the grid of the tube, you would get a cleaner brighter tone. The volume and tone can go in after that first stage.
There are better tone circuits too. That one just bleeds off some of the signal. But that's a classic amp, and will play fine as is with new caps and resistors.

Make sure this amp has a 3-prong cord attached. A low resistance path from the chassis to the house wiring might/should blow a breaker before a high voltage hits your guitar strings. Also a 1 amp fuse goes in there somewhere. Good luck.

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Burl Ives, RIP, oldtimer.
[:l>)


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