Advice needed, Fender Bassman

[Tempest]

Okay forumites, I need some advice.  Yesterday I was at an antique warehouse and of all things, there's a 1966 Fender Bassman!  It looks like it's been in storage for a while (I later learned it had been).  I asked the guy and plugged it in, the pots were scratchy and when the volume was low it was cutting in and out, only three inputs worked, and the blub was shot.  But here's the kicker, he was asking $450 for the head AND a 2x12 cabinet and I figure I could reason him down to $425 at least.  I figure if I put in a little bit of money to get her cleaned and replace some parts I can either turn it around for a profit or even just keep it.  People are listing head and cab together for over a grand on ebay.

So here's the big question, how much would you guys estimate it would cost to clean and fix one of these up?  Is it a good investment??  :help:

 

[mayfly]

It's a good investment, provided the transformers are not shot and it's cosmetically clean. Get it. Any competent tech can put it right- including me!

 

[Tempest]

How would I be able to tell if the transformers need replacing?

 

[Kostas]

You will definitely need new caps and a new power cord, so have in mind you will also spend at least $100+ if someone else does the work. If one or more of the transformers does not work there are many companies offering good replacements.

Buy it, it's an amazing amp for a very good price.

 

[mayfly]

How would I be able to tell if the transformers need replacing?

I'll give you the skinny once I have some time with a computer( on an iPhone currently)..
But what the hell- just buy it. It can be fixed.

 

[Patrick from Davis]

Yeah, at that price, you can put some money in it, play it for a good while to, "Make sure it works," and sell it later to get it all back.  Sounds, ha, like a fun time to me.  Oh, it will need a cap job, the death cap will need to be removed, and a three pronged plug should be added.  Besides that, I would stock up on a big bottle of electronics parts cleaner/contact cleaner for this, I have a feeling it will be helpful.
Patrick

 

[Tempest]

Yeah I definitely won't be doing the work haha, I have a tech that I'll bring it to, you guys are swaying me...I'm thinking I might bite on this one

 

[TroubledTreble]

I would buy it. I owned a 9/66 for quite some time before selling it. The power cord needed to be upgraded and the chassis grounded. New tubes and biasing was the only other thing it needed fortunately. It was nearly perfect and I sold it for eight. I also sold the 65' 2X12 cabinet that I also had.

I regret getting rid of it and hope to have another some day. A 2X12 cab sounds amazing with that head by the way. Does the cabinet have the tilt legs in tact? Is the attachment hardware all there?

IR of Bassman

 

[Tempest]

It appeared to have some sort of attachment to keep the head on the cab if that's what you're asking.  And yes it does have the tilt-back legs, love those on my Vibroking!

 

[Tonar8352]

BUY IT!!!!!!!! Did I say that loud enough!  :laughing7:

Now, seriously buy it fast.  That is a great price for that amp. We need pictures including pictures of the speakers. You have just been handed one of those rare opportunities to buy a great piece of vintage gear that should not be passed on.

Even if the transformers are not good which I would be surprised if that were the case you can have original transformers repaired by Mercury Magnetics.

 

[stubhead]

It's really not even safe to play around with it until a tech goes through and the capacitors have been replaced - but if you've got the money and food for a week, JUST GO GET IT.

(there's food everywhere...)

 

[Tempest]

BUY IT!!!!!!!! Did I say that loud enough!  :laughing7:

Now, seriously buy it fast.  That is a great price for that amp. We need pictures including pictures of the speakers. You have just been handed one of those rare opportunities to buy a great piece of vintage gear that should not be passed on.

Even if the transformers are not good which I would be surprised if that were the case you can have original transformers repaired by Mercury Magnetics.

How much does a transformer repair cost?  I'm just wanting to make sure I can get a return on my investment with this amp when it comes time to sell it.

 

[Tempest]

Alright, I called the guy, picking it up Tuesday, you guys convinced me!  I'll get a hold of my amp tech and see when I'll be able to take it in.  I'll be sure to get pics for all you junkies when I pick it up, but be warned, it's not exactly pretty yet!

Pretty excited!  Wish me luck this thing fixes up well.

 

[mayfly]

Congratulations!  Sure hope your tech has the ability to work on it properly and not mess it up. 

 

[Tempest]

Congratulations!  Sure hope your tech has the ability to work on it properly and not mess it up.

He's pretty darn experienced!  He's been one of the premier techs in the Kansas City area for a long time and he's worked on my Vibroking before 

 

[Alfang]

Hey how come everyone has an amp tech except me?

 

[mayfly]

Hey how come everyone has an amp tech except me?

I'll be your amp tech bayyyybeeeee  :glasses10:

 

[mayfly]

How to tell if your power transformer is shot:

This test can be done with the transformer in place.  You're looking for burnt windings.  This manifests itself in lower than expected voltages under load.  So fire it up with all the tubes in and it connected to the cab, and check to ensure:

heater rail is at a little under 6.6 VAC.
Rectifier heater rail is at 5VAC.
B+ rail is at +450VDC or more.
bias rail is at -50DC or less.

How to tell if your output transformer is shot:

This test must be done with the transformer isolated.  Fortunately, you can achieve this by removing the output tubes and speaker load.  This test must be performed with your amp turned off.  You'll also need a signal generator and an oscilloscope. 
[list type=decimal]
[*] remove the output tubes and the speaker load
[*] bleed your coupling caps to ensure there is no B+ supply voltage on the output transformer.  Ensure that this is true with a multi-meter.
[*] check the resistance on the primary (between the blue and brown wires).  It should be about 100 ohms.
[*] check the resistance on the secondary (speaker output). should be about 0.15 ohms.
[*]Connect the output (secondary) of the transformer to your signal generator.  Set it to generate a sign wave at 1KHz at 1V P-P
[*]Connect your scope between one leg of the primary and the B+ supply.  Put the ground on the B+ and the scope probe on the blue wire.  Make sure you check that the B+ is at 0V before your do this.  Have a look at the waveform.  It should be nice and clean sinusoid at about 16V P-P.  This assumes that the turns ratio is about 32:1 on that old transformer, which it should be if it's stock.  Note: this is not a general rule:  other amps will have different turns ratios.
[*]repeat the same for the other leg of the primary.  should be about the same voltage.
[/list]

If that checks out, you're good.

 

[Tempest]

How to tell if your power transformer is shot:

This test can be done with the transformer in place.  You're looking for burnt windings.  This manifests itself in lower than expected voltages under load.  So fire it up with all the tubes in and it connected to the cab, and check to ensure:

heater rail is at a little under 6.6 VAC.
Rectifier heater rail is at 5VAC.
B+ rail is at +450VDC or more.
bias rail is at -50DC or less.

How to tell if your output transformer is shot:

This test must be done with the transformer isolated.  Fortunately, you can achieve this by removing the output tubes and speaker load.  This test must be performed with your amp turned off.  You'll also need a signal generator and an oscilloscope. 
[list type=decimal]
[*] remove the output tubes and the speaker load
[*] bleed your coupling caps to ensure there is no B+ supply voltage on the output transformer.  Ensure that this is true with a multi-meter.
[*] check the resistance on the primary (between the blue and brown wires).  It should be about 100 ohms.
[*] check the resistance on the secondary (speaker output). should be about 0.15 ohms.
[*]Connect the output (secondary) of the transformer to your signal generator.  Set it to generate a sign wave at 1KHz at 1V P-P
[*]Connect your scope between one leg of the primary and the B+ supply.  Put the ground on the B+ and the scope probe on the blue wire.  Make sure you check that the B+ is at 0V before your do this.  Have a look at the waveform.  It should be nice and clean sinusoid at about 16V P-P.  This assumes that the turns ratio is about 32:1 on that old transformer, which it should be if it's stock.  Note: this is not a general rule:  other amps will have different turns ratios.
[*]repeat the same for the other leg of the primary.  should be about the same voltage.
[/list]

If that checks out, you're good.

I appreciate it!

I'll have to give that a shot with someone I know who understands how to do what you just said  :laughing7:

Thanks again to everyone for the help deciding!

 

[jackthehack]

Late to the game, but would have told you to jump on it as well... Where did you find that in KC?  Somebody had a very similar Bassman/2x12 cab with the amp nominally redone at Richard's Music in Lawrence and was asking $1200...