Re: Hoffman Fender Blues Junior Conversion

[LRX71]

While building this kit I replaced the standard Bls jr. Output trans. w/ a Heyboer T020. When I adjust the 50kl bias pot to the left, no sound and half up to full it sounds like an Octavia. What components might need to be changed to correct this? Would the Power trans. effect this as well? I haven't tried putting the original Output trans. back in yet to see if this corrects the problem. I would rather use the T020. Thanks.

[sluckey]

Swap the OT plate leads and see if that helps.

[EL34]

While building this kit I replaced the standard Bls jr. Output trans. w/ a Heyboer T020. When I adjust the 50kl bias pot to the left, no sound and half up to full it sounds like an Octavia. What components might need to be changed to correct this? Would the Power trans. effect this as well? I haven't tried putting the original Output trans. back in yet to see if this corrects the problem. I would rather use the T020. Thanks.

Do this first
http://el34world.com/Forum/index.php?topic=17701.0

What components might need to be changed to correct this?

The amp works as designed, something is not assembled correctly

[LRX71]

I wired the Red wire from the OT to the plus

• end of C25 47uf and the Brown wire of the PT to the negative [-] end of D13 In4007. Could you tell me if this is correct. Also if I damaged the PT with incorrect hookup due to some confusion on my part between the schematic and layout drawings could that be a cause of Octavia sound of the amp? Thanks

[EL34]

All you have to do is do it exactly as the schematic and layout diagram show it.


Did you do this yet?
http://el34world.com/Forum/index.php?topic=17701.0


You need to reply that you have done the above first

[LRX71]

Yes I've gone over everything. Very good method by the way. Thats why I asked about the Brown and Red wiring of the PT and OT in the previous post, just to make sure that it was correct.

[EL34]

I don't understand your question, the PDF document here clearly shows where the OT wires go
http://el34world.com/Hoffman/files/Hoffman_BluesJunior.pdf

[LRX71]

The questions I asked basically just required a simple yes or no answer. If everything on the drawings was clear to me I wouldn't be asking these questions. I just want to get the amp working again.

[EL34]

Ok, does this make sense?

Pin7 for the blue and brown wires
B+ on the main board for the red wire

Everything is color coded
These are screen shots from the Blues Junior PDF file

[LRX71]

After a few minutes of powering up the amp, while playing through it, there will be an extremely loud sound like as if I disconnected the cord from my guitar and I'm shorting it out by touching the plug end. I turn off the amp and when I fire it up again it starts doing this right away but then it goes away and I can play through the amp and its fine. This happens every time I use it and when I turn the amp off you hear two loud pops. Also,where is the voltage check points when biasing the amp? Thanks

[EL34]

There is something hooked up wrong or a connection that is loose or not soldered correctly

That's only my guess because I can't see the amp from here

You have the amp there and so you have to go over everything with a fine toothed comb using these instructions
http://el34world.com/Forum/index.php?topic=17701.0

[LRX71]

OK I will go over everything again. I also asked about biasing the Bljr. where are the test points and what voltages do you recommend?

[EL34]

You have to look all all the pages in the BJ PDF file
The voltages are listed there
http://el34world.com/Hoffman/files/Hoffman_BluesJunior.pdf


Did you read this document that is linked right below every one of my turret boards on the library page?
It describes how you build all my turret boards and how to bias them
http://el34world.com/Hoffman/instructions.htm


Please read all the documents and then ask questions
http://el34world.com/schematics.htm#Hoffman_Blues_Junior_Conversion

[sluckey]

OK I will go over everything again. I also asked about biasing the Bljr. where are the test points and what voltages do you recommend?

The test points are the actual tube sockets. Initially set the bias pot for -15vdc on pin2 of V4 and V5. If everything seems to be working readjust the bias pot for 25mV at pin 3 of V4 and V5. If the tubes are not perfectly matched you will not be able to get the exact same voltage on pin 3 of both output tubes.

These voltages are listed on the schematic.