Re: ID'ing a Fender Bassman to reverse mods

On Fri, 8 Jul 2005 00:46:52 +1000, "Phil Allison"
<philallison@xxxxxxxxxx> wrote:

>>>>I picked up a 1978'ish Fender Bassman head recently
>>>** Is it a 50 watt, 100 watt or 135 watt model ??
>> It's a 50.
> ** Now you tell us .......

Yes, I should have mentioned that before.

>>> It works and
>>> sounds good but causes shocks.
>>> ** Remove the ground switch ( 0.047uF ) cap.
>>> Consider fitting a 3 core AC lead.
>>
>> It has a grounded cord already, but I haven't verified it yet.
>
>** No way you can get "shocks" from a grounded amp and it is the amp's
>fault.

I don't think it's the amps fault. I may never know who's fault it
is, but I can confirm that it shocks me when I play through it.

>>>** Just ID the model name - it is written on the front panel !!!
>> Right. :-) It's a Bassman 50.
>
> ** You said that already.......

That's in an effort to address your points and questions completely.

>> I've got a few 50-watt schematics in
>> my copy of the Tube Amp Book, Vol 3. I figure that it's a CBS
>> circuit, but I wasn't sure if there was good way to accurately narrow
>> it down other than looking at the differences and comparing them to
>> mine manually.
>
> ** That is a good way.

That's the direction I'm going. I've rounded up four schematics that
are reportedly part of the Silverface era.

>> I guess my real question is, is there a specific circuit Fender used
>> for the 50-watt Bassman head in 1978?
>
> ** How do you know it is a '78 model ????

I don't know that it is. The amp was in reasonable shape and the
price was good, so I didn't ask a lot of questions. I was told the
original owner bought it new in 1978 when he purchased his new bass.
When it came to the technical details of the mods, things got a little
cloudy.

.

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