Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Big chief on October 03, 2020, 09:54:37 am

Title: Silver tone 1396
Post by: Big chief on October 03, 2020, 09:54:37 am

Silver tone 1396 no power to 5U4 rectifier tube or 12ax7 all other tubes light up
Low voltage on all other tubes pin 3 on6l6 should be 340 meter shows 0. 5u4 pins 4, 6
Should be 360 shows O

Any help would be great

Title: Re: Silver tone 1396
Post by: Latole on October 03, 2020, 10:28:20 am

It is not what I call low voltage. It is NO voltage  :laugh:


Schematic ;

http://schems.com/bmampscom/silvertone/silvertone_1396.pdf

Fuse is good ?
Is your meter working and is on AC scale ?

1- Do you have 120 volts at P.T primary ?  If Yes

2- Remove all tubes 5U4, 12XX7s , 6L6s All
3- Read voltage at 5U4 socket between pins 4-6. ; close 360 V ac
              "                        "                         2-8  : close o 5 V ac
    No voltage:  look P.T. is blow

4- Read winding ohms as show ;
    You will find a open winding

Title: Re: Silver tone 1396
Post by: Latole on October 03, 2020, 10:45:44 am

Schematic ;  http://schems.com/bmampscom/silvertone/silvertone_1396.pdf

Title: Re: Silver tone 1396
Post by: sluckey on October 03, 2020, 11:00:24 am

Quote from: Big chief on October 03, 2020, 09:54:37 am

...all other tubes light up
...5u4 pins 4, 6 Should be 360 shows O

Since you have filaments the PT is receiving primary voltage. But, since you have zero VAC on pins 4 and 6 of the 5U4, it's likely that the PT HT winding is faulty. You did have your meter set to read AC voltage when you checked pin 4 and 6, right?

BTW, the 12AX7s get their filament voltage from the cathodes of the 6L6s, so they will ***NOT*** be lit until you have proper plate voltage on the 6L6s.

Title: Re: Silver tone 1396
Post by: Big chief on October 03, 2020, 11:14:46 am

Have 0 on pins 2-8. 0 on 4-6 have 120 at switch 0 on fuse holder replaced fuse twice
All tubes pulled  fuse holder seems ok have .05 ohm

Title: Re: Silver tone 1396
Post by: sluckey on October 03, 2020, 11:35:21 am

Quote from: Big chief on October 03, 2020, 11:14:46 am

Have 0 on pins 2-8. 0 on 4-6

Is your meter set to measure AC VOLTS?

To correctly measure the 5VAC winding, you must put one meter probe on pin 2 and the other meter probe on pin 8. Pins 4 and 6 can be correctly measured with one probe connected to chassis.

Title: Re: Silver tone 1396
Post by: Latole on October 03, 2020, 01:17:26 pm

Answer no 1 : Is your meter working and is on AC scale ?

Look is not

Test with wall outlets

Title: Re: Silver tone 1396
Post by: Big chief on October 03, 2020, 02:33:00 pm

Meter is working and was on ac I did exactly as you stated I put test leads on 2-8 no voltage I’ll try to take some photos and post
4-6 no voltage

Title: Re: Silver tone 1396
Post by: Latole on October 03, 2020, 02:56:21 pm

Quote from: Big chief on October 03, 2020, 02:33:00 pm

Meter is working and was on ac I did exactly as you stated I put test leads on 2-8 no voltage I’ll try to take some photos and post
4-6 no voltage

PT is burn, no need more test.
You read ohms for fun on each PT coil as my screen print show

Title: Re: Silver tone 1396
Post by: Big chief on October 03, 2020, 03:24:16 pm

Thanks to all for your help will try to find a PT