It is currently Mon Mar 16, 2020 5:49 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 44 posts ]  Go to page Previous  1, 2, 3  Next
Go to page Previous  1, 2, 3  Next
Author Message
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Sun Apr 14, 2013 9:10 pm
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
I got it. It was the last 20/500 cap on the right like I thought-no pops, nice and quiet and ready to rock. I did my first complete electrolytic cap job, filter caps and all. Time for a beer. Thanks to all and to the best forum. There's nothing like a good ol' Fender. :D


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Sun Apr 14, 2013 10:17 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Outstanding.

Rawk on!

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: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Mon Apr 15, 2013 6:46 am
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
I should at least get a couple of red picks for this. Hobbyist is like a private. I should be a lieutenant. :mrgreen:


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Mon Apr 15, 2013 7:06 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Tue Jul 17, 2007 3:08 pm
Posts: 2889
You'll get there !
This place is kinda like Cheers for me without the beer :mrgreen:
Its a great place to hang out, I did my first filter cap job with the help of the guys here and have gone on to do many more and then some !
Excellent teachers here and they do it for nothing but the satisfaction of knowing another guitar player has a much better understanding of where their tone comes from 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


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Mon Apr 15, 2013 7:59 am
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
Absolutely, this is by far the best forum. Fender players are sophisticated-people who want a variety of sounds not just distortion. Leo's amps set the standard that everyone else tries to copy.


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Mon Apr 15, 2013 8:37 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Mon Feb 25, 2008 8:47 am
Posts: 2967
Location: Westchester County, NY
That's because Leo didnt want distortion, at all.


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Tue Apr 16, 2013 10:53 am
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
The stock resistors between the three 20/525 caps were 2.2K 1W and 10K 1 W. Those are the exact values for a Dual Showman Reverb. That's a big jump from 1K and 4.7K. I noticed my phase inverter 12at7 is running really hot and is making a slight popping sound again-just a few time when taken off standby. :x The tube is brand new and looks like it's been run wide-open for 10 years-black marks on the flashing. All of the Bandmaster schematics call for 1k, 4.7K resistors on the power rail. The big Sprague caps are tough, so I think I'll install the 2.2K 1W and 10K 1W resistors between the 20/525's, replace the phase inverter and see if that works better. They must have put them in to reduce the voltage. I've seen other Bandmaster Reverbs with the Dual Showman resitor values under the can on Google. What the Hellmans?


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Tue Apr 16, 2013 11:48 am
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
Also, the stock bias caps were 80/75V like twin reverbs or Dual Showmans. The Schematic calls for two 50/70's in the bias supply. So, it's Bandmaster Reverb that has filter and bias circuits that are like a twin or Showman. If I change the resistors back to stock (Twin, Showman) 2.2K and 10K, do I have to change the bias caps back to 80uf.? :?


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Tue Apr 16, 2013 2:18 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Fri Aug 21, 2009 1:45 pm
Posts: 852
Location: SoCal323
If it helps, here's a pic of my '73 BMR doghouse. When I first got the amp the resistors in the power supply were doubled in value. That brought down the volume and took away a lot of the Fender sparkle. I pulled them and went with the original values listed on the schematic and it made a huge improvement.
Eventually I'm gonna replace the filter caps with f&t. For now these are doing a good job.

Image

_________________
Its a lifestyle.....

Image


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Tue Apr 16, 2013 2:37 pm
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
Yeah, that's what mine looked for the most part like 2.2K & 10k plus the 220k with 80/75V bias caps. Every BMR schematic I've seen has 4.7K and 1K in the power rail and 50/70V bias caps. I'm confused to say the least. Oh , well. Live and learn. I'm not giving up, ever. :twisted:


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Wed Apr 17, 2013 3:21 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Krankster, changing the power supply rail resistors should not effect the bias supply circuit. Each has it's own unique tap off the power transformer. With the PS rail going throuhg a full wave bridge rectifier. The bias supply uses a half-wave (single diode ) recitification circuit.

Anyhow... I would up the voltage rating of those caps in the bias supply. 80mfd/75 caps replaced with a 100mfd/100VDC ones. This will insure constant filtering even with outlet voltage fluctuations.

:mrgreen:


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Wed Apr 17, 2013 5:29 am
Offline
Roadie
Roadie

Joined: Thu Feb 21, 2008 12:52 pm
Posts: 292
Way to go Krankster...
I have two BMRs that I modded to a Vibroverb 1 x15 and a Vibrolux 2 x10
Great amps when healthy. You will love it...

Enjoy!!!


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Fri Apr 26, 2013 12:13 pm
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
I've traced the problem to the reverb circuit. I shorted the reverb/vibrato channel and there's no popping when I take it off standby. I checked every cap, resistor, solder joint in that area-all good. Swapped out the 25uf caps and .1uf cap with known good ones even replaced the 100K 1watt resistors and a few others in the reverb circuit. The can is fine as are the braided cables. I even swapped out the last 20uf/500 cap under the can with a new one-still pops. The preamp e caps were a b##@h to get out-lots of pulling and prying. It's either a wire or one of the reverb tube sockets. Any more words of wisdom?


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Fri Apr 26, 2013 5:04 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Try De-Oxit D5 or GN5 treatment on the reverb driver & recovery tube sockets and tube pins. Also the tank and RCA jacks of the shielded cabl to and from the tank.

If that doesn't help -- try a new 12AT7 reverb driver tube. And then, a new 12AX7 recovery tube.

Good luck! Keep us posted.


Top
Profile
Post subject: Re: 1974 Bandmaster Reverb Filter Caps and Resistors
Posted: Mon Apr 29, 2013 6:59 am
Offline
Roadie
Roadie

Joined: Sat Mar 09, 2013 12:27 pm
Posts: 207
Beemer, did the Deoxit routine (good stuph) and new tubes. After going over every solder joint in the amp, touching up several, it pops twice instead of five times when turned of standby. Maybe I'm on the right track. Could new filter caps cause a weak cap or resistor to malfunction. Could a filter cap have an internal short and exhibit this symptom? Thanks, Gracias, Danke Shon, Doppi (my 2 year old daughter).


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 44 posts ]  Go to page Previous  1, 2, 3  Next
Go to page Previous  1, 2, 3  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:  
cron