Help with 67 Silveface Bassman

[woodw...@aol.com]

Hello I need some help with my 67 Silverface Bassman amp.I have a question that I hope someone can answer for me.

This amp is a 67 but some of the parts say 66.I know the Silverfaces were introduced in 67.

My question is on the bass channel the bass knob/pot doesn't sound very bassy.I turn it up to 10 and it doesn't add much boomy bass at all.

Clicking the deep switch doesn't do much either. The normal channel is better. It sounds pretty normal, but not real boomy at all.

 Could this be a tube problem? I don't know how the bass knob ties into the amp,if a tube is assigned to that knob or what.The tubes are fairly new and don't crackle or pop or make any noise .

 I was hoping one of you guys might could advise me as to what it might be.

 I have a Black Face Bassman late 66/ early 67 parts that sounds  awesome.! i was hoping/ thinking my Silver face should sound a little more

like the BlackFace.

 The Silverface makes a great guitar amp.I know many guitar players use it for that.

I appreciate any response. .

 Thanks so much,

 William Wood

woodw...@aol.com

[woodw...@aol.com]

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[kevin thomson]

Can't speak to your bass pot, but I can tell you that the knob is not assigned to a tube. Have you done a direct a/b comparison with your blackface bassman?

a 66/67 blackface should not sound any different from a 66/67 silverface....they both should have an AB165 circuit and therefore are pretty much identical....some folks into parsing the differences between capacitor brands can disagree but essentially these amps are the same....many times, two identical amps just sound diferent.

if you don't want it...write me.

enjoy....kt

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[mi...@nycap.rr.com]

Kevin,

Without looking at it there is no way that I personally could tell you what is going on. The beauty of those amps though is that they were hand made, and no sets of hands are the same. Check on the paper tag of the tube layout inside the head for what the circuit is. Probably AB165, but just verify that they are the same. Also the components most likely came from different lots or even different suppliers. A capacitor could be shorted out in the deep switch circuit(or the switch itself), or in the bass circuit, or a cap could have drifted or just be bad. I'd clean all the pots and switches, especially the deep switch, with ciruit cleaning spray. Use the lubricating kind for moving parts. A quick shot and turn the pot or switch 5 or 6 times. What you also could do is swap tubes from one amp to the other to eliminate or verify a tube problem. If you like the sound of the blackface and want the silverface to sound more like it, you could blueprint the SF to the BF, or match component by component...which would mean reading caps and resisters out of the circuit, which surely have drifted, and matching the transformers as closely as possible. Also try and duplicate the lead dress and grounding scheme. Unfortunately I don't know of any easy fix, especially for a layman....But you could probably swap the tubes and clean the pots and switches.

Mike Tremante

[woodw...@aol.com]

Thanks Kevin.I appreciate it so much.I'm learning about this amp by people like you commenting on it.I understand my Black face and Silver face are

supposed to be identical, but they do sound different to me.I know some have different circuits

I've been playing bass for over 40 years now and have owned several  amps, so I can't help but compare one  to another.I know the old tube amps have a certain sound, that's why I love them the best.

 Thanks again for the info and your knowledge.

Take care,

Will

-----Original Message-----
From: kevin thomson <thoms...@gmail.com>
To: the-amp-guide <the-am...@googlegroups.com>

[woodw...@aol.com]

Thank you Mike for the info.About all I know how to do is change out the tubes. I will try what you said, and  spray the pots too.

A few other guys have suggested some of the things you suggested too. I will try them.I do have a local guy that I use that can work on this for me if the simple steps don't work first.

I believe it is an AB 165 circuit.6L6GC, and 12AX7, and 12AT7 tubes.

 Thank you so much for responding to me.

Take care,

Will

-----Original Message-----
From: miket <mi...@nycap.rr.com>
To: the-amp-guide <the-am...@googlegroups.com>
Cc: kevin thomson <thoms...@gmail.com>
Sent: Mon, Mar 12, 2012 12:38 pm
Subject: Re: [The Amp Guide] Help with 67 Silveface Bassman

[Clay]

Will;

       If you have a copy of the schematic/layout Pin # 1 & 6 are plates(positive V), in which  are coupled(caps) to  the  next  grid#2&7 on  12ax7s-at7s.With a VOM you will read 180-200 VDC ate plates. Schematic has exact voltage. The cap is to block the DC for the next stage(tube). Test on the otherside of the cap, or the grid of the next stage. If voltage is there the cap is leaking.

Bypass caps can leak too. These are the 25ufd25vdc, and found in the first stage, and later. You must desolder the ground side of the cap only, leaving the resistor attached, and test for voltage. These are on the cathiod pin 3 &8. There is a small amount of voltage present 1.6+ on the resister, but none is to flow through the cap.

     Leaky caps will upset the next stage of the amp, and not allow it to function properly.

C.K.

[woodw...@aol.com]

Clay thank you so much for your note.I know what some of those parts are that you described but it is way over my head to work on it.

Thank you for sharing your knowledge with me. I feel like I need to take this to my amp guy to work on.I will show him what you said if you don't mind.

I think he will be able to fix the problem now that we have identified it.

Thanks so much.

[Gene Brandt]

Kevin Tomson wrote:

<a 66/67 blackface should not sound any different from a 66/67 silverface....they both should have an AB165 circuit and therefore are pretty much <identical....some folks into parsing the differences between capacitor brands can disagree but essentially these amps are the same....many times, two <identical amps just sound diferent.

 

 

 

Agree they should have exactly the same circuit, however there are always differences in production on going not recorded in documentation releases that I have found.  However,  these differences will NOT affect the sound issues you talk about, so consider them exactly the same for your question.  I still believe the blackface you have has had the bass channel modified for guitar.

 

 

Gene Brandt

 

Brandt Audio & Acoustics
http://www.baudioacoustics.com/

 

* ADA legacy products repair http://www.adaamps.com/
* Repair Guitar amplifiers, effects pedals, pro sound and studio equipment
* Custom modification of guitar amplifiers and effects pedals
* Design custom electronics for Vertex Effects Systems http://www.vertexeffects.com/
* Consulting and room modeling for acoustics and sound system design

 

2112 Knollwood Dr
Martinez, Ca
94553

 

925-890-9861
925-229-1768

 

 

 

 

[Gene Brandt]

The reason for the '66 parts is they were still in Fender inventory when they made your amp.

 

The bass & the deep switch on the bass channel will not make much difference for guitar as they are designed for bass guitar and operate at a lower frequency than normally used for guitar.

 

You can have the tone stack & switch modded for guitar if you like, keeping the rest the same, but the normal channel of the amp should work well for you, as this is what most guitarist use. 

I figure your black face amp has already been modified for guitar if it works differently as the tone stacks look almost identical per the schematics. 

Gene Brandt

 

Brandt Audio & Acoustics
http://www.baudioacoustics.com/

 

* ADA legacy products repair http://www.adaamps.com/
* Repair Guitar amplifiers, effects pedals, pro sound and studio equipment
* Custom modification of guitar amplifiers and effects pedals
* Design custom electronics for Vertex Effects Systems http://www.vertexeffects.com/
* Consulting and room modeling for acoustics and sound system design

 

2112 Knollwood Dr
Martinez, Ca
94553

 

925-890-9861
925-229-1768

 

 

[woodw...@aol.com]

Hey Kevin thank you for the nice note.I have received several messages from this board about my amp. So many great responses.I am learning about these two amps from the guys that really know them.So many have said the same things.

Let me say first that I bought the 67 Blackface Bassman in 2007, from  the widow of the man who bought the amp new in 67.He was an old black man who played soul music and R and B for many years. I was told that he never did anything to it , except play his Fender jazz bass thru it. He did change out a tube or two.I think I even have the original tubes that came with it. So , to the best of my knowledge, no one has ever worked on it.

 The Silver Face 67 Bassman I bought at a music store.It has had some work done on it....mainly tubes changed out and new caps. Just basic stuff. As far as I know no mods have ever been done to it either.I could be wrong.All I know is the normal channel sounds like a classic Fender tube amp. Everything works great. The bass channel works, but there is deffinitely no added bass "boom" when you turn the pot up to 10.It is just not there.The amp is plenty loud and works great for a guitar amp No crackle or pop or noise..However, I am a bass player. I cut my teeth on these amps 41 years ago, and I want it  to sound like it is supposed to. I just play them in my man cave, or living room. I never play them out anywhere.I just want it  to sound like the Blackface. I do understand that they are supposed to be the same. They are AB 165's.

 Thanks for all of your input. I really do appreciate it.

Takde care,

 Will

-----Original Message-----
From: Gene Brandt <tkmb...@att.net>
To: the-amp-guide <the-am...@googlegroups.com>

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