Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Big chief on October 25, 2020, 04:45:41 pm

Title: Ampeg B-15NF
Post by: Big chief on October 25, 2020, 04:45:41 pm

Have no sound to speaker all tubes light up used Ext speaker jack and used normal speaker jack.  Problem v5 flickers when touch tip of guitar cable

V1 volts pin 1-0.2 pin 2-194.1 pin 3- 1.9 pin 4-0 pin 5- 163.0 pin 6-2.3 pin7 0.6 pin 8 5.9
V2 volts pin 1-0 pin2 193.3 pin 3-1.9 pin 4-0 pin5-161.8 pin6- 2.2 pin7-0.6 pin8 5.9
V3 volts pin 1 0 pin2 237.0 pin3- 2.4 pin4 0 pin5-246.7 pin6-2.2 pin7- 0.6 pin8 5.9
V4 volts pin 2-0.6 pin3-481.3 pin4-476.4 pin5-40.0 pin7-5.9 pin8-0
V5 volts pin 2-0.6 pin3-479.4 pin4-475.1 pin5-36.5 pin7-5.9 pin8-0
V6 volts pin2-0.6 pin4-402.2 pin6-408.4 pin8-491.2

V1-3 6SL7. V4-5 6L6 v6 5AR4
Any help would be great as I’m trying to help a friend

Title: Re: Ampeg B-15NF
Post by: shooter on October 25, 2020, 05:08:02 pm

schematic
https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_b15n.pdf


looks to be an AMP out jack, tried that?

Title: Re: Ampeg B-15NF
Post by: Big chief on October 25, 2020, 06:53:24 pm

This may sound dumb I have never hooked up one amp to the other
Do You have second amp power on or off
Please tell me how to perform this task

Thanks

Title: Re: Ampeg B-15NF
Post by: AmberB on October 25, 2020, 08:13:46 pm

Is the speaker good?

Title: Re: Ampeg B-15NF
Post by: Big chief on October 26, 2020, 06:58:28 am

Speaker appears to be ok also have used ext 8 ohm jack with known good speaker.
Possible short some where at V 5

Title: Re: Ampeg B-15NF
Post by: shooter on October 26, 2020, 08:20:56 am

make it easy, got a  junk set of "powered" desktop speakers.  come up with a 1/4(preampout) to 1/8"(? speaker in), turn your amp to 1 or 2, turn powered speakers to 5, strum n listen.


or you could rebuild v5 if you think it's a problem n see

Title: Re: Ampeg B-15NF
Post by: Latole on October 26, 2020, 10:26:36 am

Do you hear hum at speaker with full volume if need ?

 You must be sure all tubes are good. Are you ?

Do you have a 'scope to follow guitar sound trough the amp circuit ? Use of signal generator is easier
No  !

 Use a voltmeter on AC scale plug at each tube input ( grid) and output ( anode )
You must read some millivolts when playing guitar.

Follow the circuit , you will see where there are no reading ; issue is there

Title: Re: Ampeg B-15NF
Post by: 2deaf on October 26, 2020, 01:09:50 pm

Quote from: Big chief on October 25, 2020, 06:53:24 pm

This may sound dumb I have never hooked up one amp to the other
Do You have second amp power on or off
Please tell me how to perform this task

You know, if you take that literally, it sounds like you are hooking the output of one amp to the output of another amp.

Title: Re: Ampeg B-15NF
Post by: Big chief on October 26, 2020, 10:31:31 pm

Had loose joint on v5 also had wire loose on speaker
Thanks for all your help
Sounds good now