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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Sep 27, 2014 7:35 am
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Chris,

100 ohm pot? Not a very big range. You sure it isn't 100k-ohms?

Just saying...


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Sep 27, 2014 7:50 am
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The schematic you posted says 100ohms also so........

I'll post a picture here in a bit

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Sep 27, 2014 8:08 am
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Chris,

I think that it is a 10k-ohm linear pot. For the Bassman 135.

-----

Image


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Sep 27, 2014 8:12 am
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yep thats the tube matching and then there is the hum balance
two separate pots

Image

Image

See the burn marks near the tabs ?

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2004 50th Ann. Limited edition AMSE Stratocaster
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1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Sep 27, 2014 9:04 am
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Chris,

Sorry about that. Haven't seen many guitar amps with a heater line hum pot. You can get close to balanced heater lines by choosing the closest 100-ohm, 1/2 watt resistors. Measure them with a DVM and find the two that match the best.

Replace the two 4.7-ohm resistors and the 100-ohm pot with your matched 100-ohm resistors on each leg of the heater line to ground. Ground the two at the same chassis point. Be sure connection to ground is secure.

The pot fried prolly due to a short in the heater line somewhere in the twisted heater line pair going to each tube's heater. This pair is usually green. Or bad contact/short on the sockets tangs.


-----

Image


Like the wiring on the Twin Reverb AA270 heater line:

http://bmamps.com/Schematics/fender/twi ... _schem.pdf


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Thu Oct 02, 2014 1:13 pm
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Got it all wrapped up , picked up and gone !
The kid brought his bass over and the thing sounds pretty good, I wasn't impressed with my Start through it, truly a bass amp in my opinion

The F&T's and a few other tidbits should give her a new lease on life, I spent a lot of time with my meter in hand looking for anything else out of spec and it was pretty solid.

I would rather stick to 50 watt pre 69 bassmans 8)

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Fri Apr 17, 2015 5:40 am
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I'm on the hunt for a Bassman head !
Lots of them out there for sale, Just waiting for the one !
Hopefully soon !
I do love talking Bassman 8)

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2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Fri Apr 17, 2015 7:10 am
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Good luck on that hunt! Here's the link (again) to Tone Lounge site, for Bassman model circuits & mods.


http://www.tone-lizard.com/Bassman_Modifications.htm


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Fri Apr 17, 2015 7:17 am
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Thanks Steve !
Or is it Larry LOL !!!

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Apr 18, 2015 2:37 am
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I've heard a guy recently playing a 1965 BF Bassman.

Its on my list since then! :mrgreen:


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Tue Apr 21, 2015 5:46 am
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I try hard to keep within a date range of 1965 to 68 if possible, look back on this (very long) thread and you'll see what CBS did in 1969 to our beloved Bassman heads, the wiring and the caps were the very cheapest junk they could find !
I rewired the entire head to get rid of all kinds of extraneous noise in my 69, the wire was so far under par its a wonder there were not a ton of house and club fires.
Looking forward to my new baby coming next week hopefully a 68 drip edge 8)

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 22, 2015 10:42 am
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Well this is a bit of a hodge podge head
1968 on the choke and the power tranny
The output is NOT a Bassman tranny
017298 # ???
E1A606-142 date code ??? (Edited to say) looks like a 1981 Fender 75 output tranny from what I've found so far.
Image

Image

Image

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Last edited by blues bondsman on Wed Apr 22, 2015 12:32 pm, edited 1 time in total.

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 22, 2015 10:44 am
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More pictures and even more when I put her back together
Dig Them Mullards ! 8)

Image

Image

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 22, 2015 12:31 pm
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I really don't care if the OT is correct or not ! I put an RCA 5751 in V-3 and a VG 12AT7 in the phase inverter
A Mullard 12AX7 in V-2 for the second gain stage
Those mullards in the power section (Great Britain / not reissues)
DANG !!! I miss that power and that tone !

here are some more pictures
Image

Needs a cap job for sure ! 1968 caps 47 years old YIKES :shock:

Image

Image

Gave the Tolex a good scrub and will do it again nest time the Chassis is out, Looks Much Better 8)

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


Last edited by blues bondsman on Wed May 06, 2015 7:12 am, edited 1 time in total.

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Thu Apr 23, 2015 7:05 am
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Not much tops a jumpered Bassman 8)
Image

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Profile
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