It is currently Mon Mar 16, 2020 10:51 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 687 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 46  Next
Go to page Previous  1, 2, 3, 4, 5 ... 46  Next
Author Message
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 6:34 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Blues, you have mail! Summarize:

1.) The heater lines have been changed. The 100-ohm resistors off the power lamp too. This maybe a sign of a previous catastrophic event.

2.) One resistor in the bias supply has been changed, As well as some wires. BUT the filter cap in that circuit seems OEM. Very odd.

3.) Defintely an AC568 circuit. You cannot simply clip the sandbox resistors without altering the bias supply voltage. This amp has that crazy hybrid cathode/fixed bias setup. Best to go back to the AB165 circuit with correct resistors and voltages. Make the balance pot a bias pot.

4.) A look under the doghosue would be nice.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 6:44 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
I hope to keep it period correct, however I did find this
http://www.mojotone.com/amp-parts/amp-t ... Ps0ph1LWSo
Just in case we don't find an original

Now for some proper cloth covered wire a 110 outlet and a proper three prong cord.

a few more pictures of the circuit
Image
Image

I believe its been changed to a bias adjust ? not a hum balance, tube matching device.

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 6:52 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Hey Beemer posted the pics you asked for earlier see above

How about this if an original can't be found.

http://www.classictone.net/40-18011.html

My goal is to restore to an AB-165

You guys are making me feel better all ready, one of the power tubes had a broken indicator pin and won't idle under 45ma the other was sitting pretty at 32ma

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:13 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Blues... Beaver cap? Not going to go there. The other Mallories seem to be original. Why the tech didn't replace, at least, the TWO caps in the first filter stage is beyond me.

Classic Tone tranny is prolly close to what is in the amp now.

I like Hammond or Mojo Tone.

http://www.mojotone.com/amp-parts/trans ... ransformer

http://www.hammondmfg.com/pdf/EDB1760L.pdf

BTW... from your photos --- the bias circuit seems to be OEM AC568. Not AB165. The whole wiring would need to be redone to be period correct.

http://www.webphix.com/schematic%20heav ... _ac568.pdf


Last edited by BMW2002Ti on Sat Jan 19, 2013 7:22 pm, edited 1 time in total.

Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:18 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Please excuse my ignorance :roll:
What do you do with the other "taps" for 8 and 16 ohms ?

The one in there now is about half the size of the original

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:28 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Blues, I wind them up and seal the ends with heat shrink. Stuff them into the chassis, somewhere safe. Then, if you ever change the speakers, you have the proper impedance. Or you can cut them. And place heat shrink onto the stubs.

I have this feeling that isn't a proper Bassman replacement tranny. As most I've seen are bigger than usual dual 6L6GC OPTs. This is really whre a lot of the Bassman tone lies. In that iron. So, a proper replacement. Or the real thing would be nice.

As for push-back wiring. There are places that sell this. Please avoid Chinese made stuff, if possible.


http://www.stewmac.com/shop/Electronics ... _Wire.html


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:35 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
I'm going to have one serious parts list !
Guessing I'll have a lot of the carbon comps that I'll need from that last blackface Bassman you guys helped me through.

Looking at the board, there are a lot of rough looking resistors and turd caps

Might as well go all the way and make this thing sweet !!!

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:36 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
PS I had gotten an extra bias Pot also during that last fix and this one is stuck from the bottom, turns fine inside the chassis.

This is gonna try my abilities at reading schematics and layouts !!!

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 7:40 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Blues, that's what I'd do. Even if it takes awhile. IMHO this amp is worth the effort. And any NOS tube will thank you! :D Best to study the two schemos & layouts involved, prior to making that list.

You known, this is the first amp I've seen where the LAST filter cap (20/525) was replaced, but no other one was. Very odd... :?:

Good luck! Be an interesting Winter/Spring project.

http://www.webphix.com/schematic%20heav ... _ac568.pdf

http://www.webphix.com/schematic%20heav ... _schem.pdf


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Jan 19, 2013 9:05 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
If I thought I wouldnt forget something I would disassemble the entire board pots etc... and start over :wink:

However I'm one of those people who walk into a room and forget why I went there.

I printed those last two documents THANKS !!!

I believe Arjay is on the hunt for an original 022871 tranny with me, and so yes I'll be taking a lot of time with this project and lots of reference pictures.

Funny how much corrosion seems to be in the chassis ! I'm betting your assumption that there was a major failure it this amps past.

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Jan 20, 2013 9:52 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Blues, the corrosion marks kinda look like the effect of a 'lytic cap leaking. Or tranny potting fluid overheating and spilling out. These fluids are the more corrosive, of components.

BTW... that twisted pair of white wires from the lamp to the 6L6GC heaters is much too small gauge. Should be same gauge as the green ones coming out of the power tranny. These lines carry the heaviest current in most tube amps.


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Jan 20, 2013 10:06 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
so 22 gauge or 18 ?

_________________
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


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Jan 20, 2013 10:26 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Go with green push-back 18 gauge to the 6L6GC. Then, 20 gauge from the 6L6GC to the 12AT7 & 12AX7s. I used a drill and insert the two lines into the chuck. Then, SLOWY turn the wires to get that nice even looking twist.

Image

Image


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Jan 20, 2013 11:49 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26416
Location: Tombstone Territory
That's a great looking wiring harness, Steve!

8)

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Jan 20, 2013 1:02 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
Ya Steve !
Thats how i want mine to look !!!!

Would you guys think it might be better to get a new eyelet board and populate it then install it ?

The wiring is so sloppy now I wonder if I'll ever get it straight :(

_________________
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


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 687 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 46  Next
Go to page Previous  1, 2, 3, 4, 5 ... 46  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: