Issue With Bassman 5F6A Build

[Guitarnut]

Yes, 2 and 7, the grids, but resistance to ground.

The measurements are from each pin to ground.

1029K on 2 and 1016K on 7. Pretty close to 1014K.

I have the inputs rewired and I'll post numbers in a few.

Peace,
Mark

[martin manning]

Ah, I forgot that I already asked; sorry.

[Guitarnut]

Ah, I forgot that I already asked; sorry.

No problem.

Peace,
Mark

[Guitarnut]

New numbers on the rewired inputs.

Jack hots to ground. Jack inserted.
Norm Jack 1 1036K
Norm Jack 2 144K
Bright Jack 1 1041K
Bright Jack 2 140K

V1 screens to ground. Jack inserted.
Normal Jack 1
pin2 1100K pin7 1100K
Normal Jack 2
pin2 76K pin7 1100K

Bright Jack 1
pin2 1085K pin7 1100K
Bright Jack 2
pin2 1085K pin7 74K

Hopefully this is some progress.

Peace,
Mark

[martin manning]

Those look odd...

When you jack into Normal input 1, you should see

1M to ground from the hot/tip of the plug
1034k to ground from the grid of the Normal triode (pin 2)
34k to ground from the grid of the Bright triode (pin 7)

When you jack into Normal input 2, you should see

136k to ground from the hot/tip of the plug
68k to ground from the grid of the Normal triode (pin 2)
34k to ground from the grid of the Bright triode (pin 7)

When you jack into Bright input 1, you should see

1M to ground from the hot/tip of the plug
1034k to ground from the grid of the Bright triode (pin 7)
34k to ground from the grid of the Normal triode (pin 2)

When you jack into Bright input 2, you should see

136k to ground from the hot/tip of the plug
68k to ground from the grid of the Bright triode (pin 7)
34k to ground from the grid of the Normal triode (pin 2)

Edit: corrected resistance to ground from grid of input not in use

[martin manning]

The layout here shows the jack wiring: https://tubeamparchive.com/viewtopic.ph ... 321#226321

It looks like the Weber(?) layout posted earlier does have the #1 and #2 jack numbers swapped viz. the original Fender.

[Guitarnut]

The layout here shows the jack wiring: https://tubeamparchive.com/viewtopic.ph ... 321#226321

Thanks! Excellent information there. Part of the confusion I think I having on following the common diagrams is the jacks Mojo sent me have the ground lug in the center...this doesn't match up with any of the drawings and I'm sure I'm transposing something incorrectly.

Peace,
Mark

[Guitarnut]

I think I'm at the back up and start over stage. I just keep chasing gremlins and despite the excellent troubleshooting ideas from you fine folks, I'm not making much headway...purely my own fault.

I'll strip down all the sockets, remove the bulky caps from the board and check every solder joint and resistor value. I may take pics as I wire the sockets so you guys can follow along.

I have new sockets, caps and resistors due in tomorrow to cover me on anything that's out of spec or heat damaged. If none are needed, I'll have some goodies for the next build.

It's Friday night and I'm going to step away, have some hot pizza, a few cold beers and watch a movie with my sweetie.

I'll be back at it tomorrow.

Thanks again for all the guidance and education.

Peace,
Mark

[JazzGuitarGimp]

I think I'm at the back up and start over stage. I just keep chasing gremlins and despite the excellent troubleshooting ideas from you fine folks, I'm not making much headway...purely my own fault.

I'll strip down all the sockets, remove the bulky caps from the board and check every solder joint and resistor value. I may take pics as I wire the sockets so you guys can follow along.

I have new sockets, caps and resistors due in tomorrow to cover me on anything that's out of spec or heat damaged. If none are needed, I'll have some goodies for the next build.

It's Friday night and I'm going to step away, have some hot pizza, a few cold beers and watch a movie with my sweetie.

I'll be back at it tomorrow.

Thanks again for all the guidance and education.

Peace,
Mark

Hi Mark,

I've been following along and I think this is a good idea. I suspect you are getting to a place in your soldering where you are beginning to recognise the difference between a good-, and a bad-solder joint. Good luck with the rebuild. I have a feeling it's going to come out just fine this time.

Regards,
Lou

[martin manning]

I must say you don't give up easily! I would ditch those jacks and get some Switchcraft 12A's. I didn't notice the them before in your photos. That would be very confusing indeed, and yet another strike against Mojo... TRS jacks? WTF?

[Reeltarded]

Mojo pushed Martin too far this time!

They Ganked Steve Miller's loop too. I will never buy anything from them again.

[ToneMerc]

I must say you don't give up easily! I would ditch those jacks and get some Switchcraft 12A's. I didn't notice the them before in your photos. That would be very confusing indeed, and yet another strike against Mojo... TRS jacks? WTF?

Now you see why I dont recommended Mojo kits in general; poor or inaccurate documentation, poor part selection, fitment, layout, etc. Although I have used chassis, pots and cabinets which are good, matter of fact I placed an order yesterday morning and it arrived today.

My impression is that their kits are more aligned to builders, than drop in assembler types.

In all honestly, having just finished a narrow Tweed chaasis build, this style of chassis is not the friendliest to work in and it requires a bit of planning in order of sequence.

TM

[M Fowler]

In all honestly, having just finished a narrow Tweed chaasis build, this style of chassis is not the friendliest to work in and it requires a bit of planning in order of sequence.

Too many people building these tweed amps and they are not an easy paint by number amps to be building if you don't have experience.

Stop this madness.

[martin manning]

My experience is similar to TM's, and (as I have previously ranted) they are at the bottom of the list of places I go for parts. I agree the chassis is tight, but that is reason for more careful part selection and detailed assembly instructions, not less.

From the attached document, what is the primary impedance of their 5F6-A OT as-drawn? Answer: 8k!

[Guitarnut]

Hi Mark,

I've been following along and I think this is a good idea. I suspect you are getting to a place in your soldering where you are beginning to recognise the difference between a good-, and a bad-solder joint. Good luck with the rebuild. I have a feeling it's going to come out just fine this time.

Regards,
Lou

Thanks Lou! I'm definitely more confident going back in this time.

Peace,
Mark