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Post subject: Silverface Bassman questions
Posted: Tue Jul 27, 2010 8:37 am
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So I just bought a silverface Bassman. I've been trying to date it but the number stamped on the metal chassis is A73867 which all the dating info that I can find on the web seems to not cover which is a shame. However I did get some numbers from the big metal boxes inside the amp - I assume these are the transformers - these are:

J022822 606 0673 CSA TEST
022699 - 606 - 5 - 04
022871 - 606 - 4 - 01

From what i've read that first number could point to 1973 and the other 2 point to 1965 & 1964 which seems odd. Is anyone able to shed anymore light on this?

I also have a few other questions that i'm hoping that people can help me with.

There is a ground switch on the back, what is this for and what should it be set to for use in the UK? The amp has a regular UK 3 pin mains plug.

Would it be safe to run an 8 Ohm cab from the Bassman?

Each channel has 2 inputs, are they the same or is one for a bright input like other modern amps tend to be?

Any idea of an easy way to tell what circuit it has?

Sorry to ask so many questions, if anyone can help it would be most appreciated.


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Post subject: Re: Silverface Bassman questions
Posted: Tue Jul 27, 2010 9:03 am
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Data from this site......

http://www.superiormusic.com/page195.htm

......Suggests that this amp is a 1977 model.

Does the front panel read "Bassman 50", "Bassman 70" or "Bassman 135"?

Does it have a master volume control?

If the amp has a grounded 3-conductor power cable the "ground" switch on the rear panel is unnecessary and its setting is immaterial.

An 8Ω load is safe for this amp but it's actually optimized to see 4Ω unless it's a "70" or "135" version -- those variants can safely run at 2Ω if the load is split between the primary and extension speaker jacks.

The dual inputs on each channel are intended for high/low gain applications. The "1" position should be used with passive pickups while the "2" should be reserved for instruments with active electronics.

As to the type of circuit, I can better tell you what it's not......

It is not a 6G6-A, an AA864, or an AB165. And silverface amps made subsequent to 1971 used no specific circuit revision or designation, at least until late '77 when the first "ultra-linear" circuits appeared.

Some pics would help to confirm your amp's ID if you can manage them.

Best of luck, HTH

Arjay

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"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


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Posted: Tue Jul 27, 2010 9:09 am
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Thanks for the info. The front panel reads Bassman 50 and it doesn't have a master volume control.

How can I tell if it has grounded 3-conductor power cable? I know nothing about electronics i'm afraid.

I don't have any pics but they can be seen on an old ebay posting from the guy I bought it off, I think these can be seen at the following link but I can't check as i'm at work and I can't look at ebay. http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWAX:IT


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Posted: Tue Jul 27, 2010 9:12 am
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Also re the chassis number, mine starts with a 7 and has 4 digits not 5 as that website says which was where I was confused.


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Posted: Tue Jul 27, 2010 9:28 am
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The accompanying small-box speaker enclosure shown in the listing (if original to that particular amp head) would date your chassis to '75 or later, which is consistent with some of the tranny codes.

Amps from this era were all factory-equipped with grounded power cords so that should not be anything to fret over unless it's been monkeyed with.

If you have concerns over safety and/or reliability issues take it to a qualified amp tech prior to placing it into service. I can recommend someone in London if you wish.

HTH

Arjay

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"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


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Posted: Tue Jul 27, 2010 11:18 am
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Thanks Arjay.

I don't know if it makes any difference but the listing said it came with a 2 x 10 cab which is incorrect as the cab has 2 x 15 speakers.

Thanks for the offer of pointing out a good amp tech in London, the guy I go to trades as Guitar Aid and is based near Putney Bridge - i'm going to drop it round on thursday when I pick up my Carlsbro 50 Top that he has just serviced for me.


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Post subject:
Posted: Tue Jul 27, 2010 11:34 am
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Sounds good, JS. Let us know what your tech has to say.

Arjay

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"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


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Posted: Tue Aug 17, 2010 3:48 am
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I've just had the amp serviced and new power tubes fitted and it sounds awesome. My tech also found out what circuit it has and it's an AB165 which is apparently a good one according to him however i've never played any other Bassman so have nothing to compare it to.


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