Kent 3 tube Vintage practice tube amp/ HELP ME IDENTIFY!!!!!!!

[JHow]

right,how do you test it? I was thinking of replacing it with a better newer one

I don't have the link handy but do a google search for " geofex testing output transformers". The esteemed RG Keen is the site owner of geofex . He often posts here, and his info on transformers is good info.

[RitzRed]

ok I will check him out, I got a little amp that came out of a record player I am going to try to make it into a small practice amp but that is another project do you know anything about making a guitar /harp amp from one of these?

[JHow]

ok I will check him out, I got a little amp that came out of a record player I am going to try to make it into a small practice amp but that is another project do you know anything about making a guitar /harp amp from one of these?

Well that's why i was laughing at myself upstream because your Kent pretty much IS the same amp as my old RCA record player. Personally, though I think it's best to keep record players and radios for their original purposes, especially if it works. At the most basic level, All you needis an input for guitar where you now have the input from the cartridge. Do you have a schematic?

[RitzRed]

no all I know about it is that it is a magnivox and it was already out of the cabinet when I got it. I am working on a schematic for the Kent right now or I should say I am copying one I found it has all the same tubes except the 12AV6 is a 12AU6 in this schematic . is that going to make allot of difference ? looking at the schematic and the amp they seem to be the same oh yea and this schematic has 2 transformers I am wondering now if this amp with the schematic I am copying is a widow maker as well ? seeing as it has 2 transformers

[JHow]

...I am working on a schematic for the Kent right now or I should say I am copying one I found it has all the same tubes except the 12AV6 is a 12AU6 in this schematic . is that going to make allot of difference ?

They are not inter-changeable. one is a triode, the other pentode. They work differently and are supported by different parts. Even the same tubes can be set up differently, depending on how they are biased. Also pin-outs are different.

But the solution to your problem is right in front of you... assume you have 12av6...draw the symbol for the tube... draw all the parts connected to the grid, cathode, plate by looking at the parts in front of you. Don't worry too much about values if you can read the codes on the caps or resistors, just draw the symbol in the appropriate place as you see the connections in front of you. It's good exercise.

...oh yea and this schematic has 2 transformers I am wondering now if this amp with the schematic I am copying is a widow maker as well ? seeing as it has 2 transformers

No, you cant assume that two transformers does not equal widow maker. Have a look at the harmony 400 at schematic heaven (link below). T1 is output transformer, T2 isolates the 12V heater of the preamp, which is better than without but still not full isolation. You have to look at what the transformer in question is doing.

http://www.webphix.com/schematic%20h...rmony_h400.pdf

Here are links that I collected previously on this topic. The first schematic I ever hand drew (before the internet) was a transformer less Philco radio. I have about four or five of these still. I always liked the cheap stuff, I guess.

http://music-electronics-forum.com/t10852/

http://music-electronics-forum.com/t16390/

1960's Harmony H400A - The Gear Page

isolation transformer won't supply filiments - 1968 Harmony H400A tube guitar amp - diyAudio

Isolation transformer upgrade for old guitar amps

Triad Magnetics - N-68X - Power Products - Transformers - Allied Electronics

Choosing an isolation transformer

[RitzRed]

yea I am pretty sure this schmatic I am working on now is the right one how much difference is between the components when you have a 12AV6 or 12AU6 like I said before this amp came with a 12AV6 , 50C5 and 35W4 the schematics I am working on has the 35W4, 50C5 but this one has a 12AU6 instead of the 12AV6 does the V and U make allot of difference? I am still looking for the parts you suggested

[Jazz P Bass]

[QUOTE=RitzRed;280357]yea I am pretty sure this schmatic I am working on now is the right one how much difference is between the components when you have a 12AV6 or 12AU6 like I said before this amp came with a 12AV6 , 50C5 and 35W4 the schematics I am working on has the 35W4, 50C5 but this one has a 12AU6 instead of the 12AV6 does the V and U make allot of difference? /QUOTE]
I sincerely doubt that a 12AV6 tube belongs in this amp.The 12AV6 & the 12AU6 are totally, totally different tubes.
The 12AU6 is a pentode tube.
the 12AV6 is a diode & one triode.
I really do not see where a diode would be used in a guitar amp.
I have attached the two datasheets.
Compare the amp to them.
Both have pin 3 & 4 as heaters.
If it is a pentode, then pin 7 should go to ground.

[RitzRed]

yea well they must have wired this amp like a radio or record player . the 12AV6 # 7 pin is wired to the on/off switch and the multi tube the big orange paper tube it is a red wire that is jumped to the middle socket #6 pin there is also a resistor there that jumps pin to pin the green wire out of the multi tube goes to that #6 pin

[Jazz P Bass]

Where do pin 5 & pin 1 go to?

[RitzRed]

#5 goes over to the strip through a resistor #4 goes to the same place on the strip through a rectangle ceramic resistor #,s 1,2,and 6 are empty

[JHow]

Jazz P: As odd as it sounds, I think he does have a 12av6 in the pre-amp. Up in post #16 he described the hookup on that tube as:

bottom tube socket pin#1 has a .015 mfd tone cap and a resistor both are going back to the strip #2 pin has a black wire going to the volume pot and a resistor to the strip,pin # 3 has a resistor to the strip and a jump wire to the strip back where the resistor from the middle socket pin#2 connects pin #4 jump wire back to middle socket pin#3 pin#5and#6 are bare fineally pin#7 of course has the tone cap.047 mfd 200vdc bact to pin#1 middle socket

This sounds to me like pin #1 is grid, input. Pin #2 is cathode going to a common ground, pin #7 is plate with cap (and should have anode resistor somewhere) to next stage, and pins #5 and #6 are unused because those are the diodes, and the heaters are #3, and 4 for all these tubes.

If he had 12au6 pin 7 would be cathode (no cap), and 5 would be plate (would want to see a cap and a resistor) and 6 would be screen (with a resistor somewhere near).

[JHow]

#5 goes over to the strip through a resistor #4 goes to the same place on the strip through a rectangle ceramic resistor #,s 1,2,and 6 are empty

Hmm, is that for the 12-series tube? Pin #1 is grids for 12av6 or 12au6, and it is cathode for 50C5, in all these tubes pin 1 has an important job and should be connected to something.

[RitzRed]

you know I think maybe they sent the wrong tube so I am going to look through my other amps to see if I have a 12AU6 if not I will buy one then try that .in the place where the 12AV6 is you do know that I am not sure witch tube goes where rite

[JHow]

Double-check your counting of pins. Looking from the bottom, counting from the "gap", pins go clockwise 1-7. Jazz P and I are saying the same thing, figure out where pin 7 goes, or give us a good shot of the preamp socket straight on.

[RitzRed]

try this let me know if you need more pics or different ones