Tube depot clone

Lowerleftcoast

Poster Extraordinaire
Joined
Dec 30, 2019
Posts
6,042
Location
california
it is wired wrong the red wire from the board hole label J is going to pin 2 with the heaters it is supposed to be on pin 1 . So this could be the problem with both resistors burning up , I will change it but can someone describe to me how this is doing what it is doing and not being a short or blowing up the transformer I just want to know what other kind of damage have i done did I mess up the tubes thanks again for your help
The 6.3V heater is AC power with a center tap connected to the chassis. When the board terminal *J* was connected to the heater wire, the B+ at terminal *J* had a direct route to the chassis through the heater center tap. The 4.7k dropping resistor was the only resistance between the B+ and ground. It was overloaded. This short would stress the wiring (including the PT coil) and the rectifier tube. The power tubes probably were not stressed. The PT heater coils have larger wire and less turns than the HT coil, so the HT secondary would take the harder hit. Chances are the PT is OK. PCB traces, the 4.7k resistor, and the rectifier tube could be damaged.

Imo, the V1 cathode resistor should not have been involved with this terminal *J* short. Something is mis-wired at V1 as well.

Since you are familiar with electricity, think of the DC as just a battery. (The B+ terminology comes from "battery positive".
The *battery* is rectified AC, so the HT secondary of the PT, the rectifier, the reservoir capacitor, and the HT center tap, make up *the battery*. There is *positive* and *negative* so all of the DC wiring is just like wiring a DC light bulb or buzzer. The light bulb or buzzer are *loads*. The tubes in the amplifier are just *loads*.
 

andrewRneumann

Friend of Leo's
Joined
Mar 22, 2020
Posts
2,154
Location
Cincinnati, OH, USA
Ok I get it I will continue looking at the wiring and hope that the traces are good thank you for explaining it to me

Specifically on V1, look at the jumper between pin 3 and 8. Make sure it isn’t miswired or shorting to something. Also figure out what is going on with that solder lug that doesn’t look attached properly which I circled in the photo.
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
Ok I will have to check that tonight when I get home from work I got about two hours before I call it a day
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
I finally got to get some time on the amp repair, I moved the wire to the correct pin on V3 and replaced the burnt up resistors what should I check now or test now before I charge it up turn it on
 

Lowerleftcoast

Poster Extraordinaire
Joined
Dec 30, 2019
Posts
6,042
Location
california
There was also a problem at V1 so, check all of the connections there before powering up tests.

FYI to call/notify other members, type in the *at* sign with their user name. Leave a space after their name or it won't give them a blip in the *alert* box.
I will do it for you this time. @andrewRneumann @tele_savales @D'tar

You can also alert other members by replying to their post.
 

D'tar

Friend of Leo's
Joined
Jan 11, 2013
Posts
3,851
Location
WNY
I beleive you will find issue if you understand and complete the resistance checks found on the @andrewRneumann worksheet posted early in the thread. Do you know the color code for a 100k resistor @V1 plate load? It's not brown-black-brown. Use that worksheet and your meter. Youre almost there!

1666191168086.png
 
Last edited:

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
There was also a problem at V1 so, check all of the connections there before powering up tests.

FYI to call/notify other members, type in the *at* sign with their user name. Leave a space after their name or it won't give them a blip in the *alert* box.
I will do it for you this time. @andrewRneumann @tele_savales @D'tar

You can also alert other members by replying to their post.
Ok thank you for explaining that to me ok I will have to get to the other test for V1 glad I didn’t power it up yet thanks I will get back to you.
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
Ok thank you for explaining that to me ok I will have to get to the other test for V1 glad I didn’t power it up yet thanks I will get back to you.
Ok I did the resistance / ohm testing like the chart said too this is what I came up with.
 

Attachments

  • image.jpg
    image.jpg
    169.6 KB · Views: 12
  • image.jpg
    image.jpg
    157.7 KB · Views: 12
  • image.jpg
    image.jpg
    156.2 KB · Views: 13
  • image.jpg
    image.jpg
    135.1 KB · Views: 13

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
Pin 4 on both power tubes just kept increasing and increasing so it’s more than 12M
The resistor next to the F on the board measuring 99.4K and the other resistor to the left of that one closer to the letter E on the board measuring 55.4k
 

D'tar

Friend of Leo's
Joined
Jan 11, 2013
Posts
3,851
Location
WNY
One issue may be that you have 100k resistors for your heater center tap and 100 ohm resistors for plate load at V1. If heater pins to ground measure 50k. On the sheet, be sure to note where the leads of your meter are placed, for instance V1, p1 to B+ (not to chassis).
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
One issue may be that you have 100k resistors for your heater center tap and 100 ohm resistors for plate load at V1. If heater pins to ground measure 50k. On the sheet, be sure to note where the leads of your meter are placed, for instance V1, p1 to B+ (not to chassis).
So where should I get the b+ What I did put my black meter lead on the chassis and the red lead to the pins of the tubes where the pins on the tube plugs into the socket . What is 50k mean in that position , is that too high ? I tested the two resistor in that one picture one was 99.4 so that’s good a 100 k the other one was not 100 k I’ll have to check that one maybe that is why resistor r9 burnt up ? ? ?
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
Wi
I beleive you will find issue if you understand and complete the resistance checks found on the @andrewRneumann worksheet posted early in the thread. Do you know the color code for a 100k resistor @V1 plate load? It's not brown-black-brown. Use that worksheet and your meter. Youre almost there!

View attachment 1041739
With my multi meter I got 99.2&99.1 ohms on these two resistors
 

andrewRneumann

Friend of Leo's
Joined
Mar 22, 2020
Posts
2,154
Location
Cincinnati, OH, USA
The resistance measurements for plates and screens always go back to B+ (the first filter cap right after the rectifier, positive end). Cathodes and control grid resistance measurements go back to chassis. My chart tells you which ones to measure to B+. Try that and report back!
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
I beleive you will find issue if you understand and complete the resistance checks found on the @andrewRneumann worksheet posted early in the thread. Do you know the color code for a 100k resistor @V1 plate load? It's not brown-black-brown. Use that worksheet and your meter. Youre almost there!

View attachment 1041739
So it looks like R7 and R8 I put the wrong value resistor in I have each one is 100 ohms each actually 99.4 instead of 100k resistor I bet this is my problem with V1
 

dan40

Friend of Leo's
Joined
Aug 19, 2015
Posts
2,947
Location
Richmond Va
With my multi meter I got 99.2&99.1 ohms on these two resistors

As D'tar mentioned above, those two plate resistors should be 100k not 100 ohms. It appears that you accidentally used your 100k plate resistors for your artificial centertap on the filaments and you used the 100ohm resistors for the v1 plate resistors. These need to be swapped before proceeding.
 

Fixer2

TDPRI Member
Joined
Dec 25, 2020
Posts
90
Age
53
Location
NewYork State
As D'tar mentioned above, those two plate resistors should be 100k not 100 ohms. It appears that you accidentally used your 100k plate resistors for your artificial centertap on the filaments and you used the 100ohm resistors for the v1 plate resistors. These need to be swapped before proceeding.
Ok will do. The one resistor measured only 55k not a 100 k but I will get a another 100 k so they will be close to each other in value but more important 100k I can’t believe I mix them up
 

D'tar

Friend of Leo's
Joined
Jan 11, 2013
Posts
3,851
Location
WNY
Ok will do. The one resistor measured only 55k not a 100 k but I will get a another 100 k so they will be close to each other in value but more important 100k I can’t believe I mix them up
The 100k resistors used as the heater center tap are being measured in parallel while connected to the circuit. Remove them and recheck. You will likely find they are of the correct value. Not correct for heater center tap, but correct 100k
 
Last edited:




New Posts

Top