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Post subject: Re: Blackface bassman 1967 AB165
Posted: Mon Mar 05, 2012 12:17 pm
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blues bondsman wrote:
...

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Whats the very best replacement ?


Lots of good ones, Mallory, Sprague, F&T, others. I would consider replacing all of the electrolytics on that board as they look like forty-five-year-old originals.

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Mon Mar 05, 2012 4:54 pm
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Where do I get said Caps ?

Man this amp sounds so amazing (maybe I said that)
I hate to change a thing, from the cap drool in the cover that cap has been leaking a while, Why no noise ???

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Mon Mar 05, 2012 9:13 pm
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Blues, you can go to: tubesandmore.com. There are plenty of other sources for your needs. Why isn't it making noise? My guess would be that it is affecting the sound. After the recap, you should probably stand back a few more feet ! Don't forget the bias cap and check the screen resistors before ordering parts( in fact check all the power supply resistors). Good Hunting & Pickin' ! Art

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Last edited by aclempoppi on Tue Mar 06, 2012 1:17 am, edited 1 time in total.

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Mon Mar 05, 2012 9:15 pm
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Looks like one of the 20 uF, the schematic list 525 volt for the 20 uF caps.

If the schematic is correct, you should have three 20 uF 525 volt, two 70 uF 350 volt (value not clear on the schematic), and one 8 uF 450 volt. If the 20 uF are rated 525 volts, then the 20 uF 600 volt replacement at AES will work.

Check AES under Capacitors> Electrolytics> Sprague Atoms>, select the value
http://www.tubesandmore.com/

The schematic isn't very clear, but looks like two are 70 uF and 350 volt rating. If so, there are 80 uF 450 volt Spragues on the AES site that will work. Either way, check the label on the caps for the values, and AES probably has one that will work. Double check the length of the caps to be sure that the Spragues will fit (I think that they will).

Edit:
The bad cap/caps, might be giving you some pleasing distortion and/or loss of headroom, as aclempoppi indicated.

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Last edited by shimmilou on Mon Mar 05, 2012 9:20 pm, edited 1 time in total.

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Mon Mar 05, 2012 9:18 pm
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aclempoppi wrote:
in fact check all the power supply resistors


+1

Everything under the doghouse should be measured by meter and visually inspected. Parts exhibiting excessive component drift should be replaced.

Arjay

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 6:54 am
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I get exactly what you guys are saying.
The problem is, I have never played an amp with a bass response like this one, Never!
I would think the bass would start getting flabby as all get out and its not.
Maybe its just the fact that I've been playing tube rectified amps so long, the bassmans response to my playing is what I'm Digg'n
It seems as if it takes less effort to dig out the notes and tones I want from my strat.
Putting a soldering iron to this amp isn't something I really want to do.

Sure wish i lived closer to one of you fellas ! dang Hoosieritis has me stuck here

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 9:15 am
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Blues, we'll be there (in spirit) when you replace those caps. BTW... WATCH THE POLARITY under the hood. I actually mark the (+) and (-) sides and try to pull and replace one cap-at-a-time. Many Bassman (and other Fenders) flip one of the larger 70mfd/350VDC caps.

FWIW... I've been using WW low inductance resistors in the PS rail for some time. Stable & quiet. They seem to react to transients better (= even better bass). :)

Also, helps to ramp-up new caps. For two reasons. Most important, checks for mis-wiring before damage. And two, you just never know how long a cap maybe sitting on a vendor's shelf. Re-forming it never hurts. Often extends life.

Variac is nice, but old electrician's inline lamp-trick works just as well. Good luck!

http://antiqueradio.org/dimbulb.htm


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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 9:42 am
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O.K. (says with trembling hands) LOL !!!

Please teach me how to make the cap discharge thingy again.

Thanks Guys !!!

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 10:31 am
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Get a 150-500 ohm "sandbox" (wirewound) 5-10 watt resistor. Solder two 3-5 inch leads to each end. Attach alligator clips to leads.

Unplug power line. Clip one lead to chassis. One lead to (+) end of any power supply cap. Turn the "standby" switch as if powering on. At 150 ohms, should take a second to discharge. With amps that have BIG OPT, leave discharge resistor in place, as sometimes there will be residual voltage due to decaying magnetism in the OPT.

Be SURE to remove draining resistor before firing up unit.

Good luck! Hopefully, no 4th of July "treats." :mrgreen:

http://www.ebay.com/itm/150-ohm-10W-Pan ... 0640140148


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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 11:44 am
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how about this one ?

Dale HLW-12-A1Z Resistor 12W 150 ohm 5% 150Ω NEW

says its wire wound


what should I do to clean up the leaked cap contents ? anything special ?

Thanks

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 4:30 pm
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BMW2002Ti wrote:
...Turn the "standby" switch as if powering on....


Completely unnecessary to use the standby switch when draining caps using a resistor. The negative of all caps are to ground already, and the drain resistor connects the positive of the caps to ground through the resistor. The standby switch does nothing when amp is powered off. :idea:

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 4:36 pm
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shimmilou wrote:
Completely unnecessary to use the standby switch when draining caps using a resistor. The negative of all caps are to ground already, and the drain resistor connects the positive of the caps to ground through the resistor. The standby switch does nothing when amp is powered off. :idea:


Correct.

Arjay

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 5:26 pm
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Blues, IMHO, First, draw a diagram(layout) of the filter-cap board, including cap polarities, cap values, wire color codes, and resistor codes( the 220k's are located under the 70-350's). I tend to plan my work and write down the process before starting any job. That way, I have a check list to look back on, and provide myself or the customer a record. After desoldering, I clean the boards with Deoxit D-5 and a tooth brush. Now, with the '67 you may find cap wires running underneath the top circuit board, this would have to be in your diagram! This technique is sanitary, but inconvenient. If you choose to leave the wires in place, then you can make soldering loops or use the eyelets near the new cap location, and make the connection above the board. Just take your time and plan ahead ! Good Luck, Art

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 5:48 pm
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+1, Art.

Alternatively, shoot a pic of the cap board showing the condensor array and their polarity, then print out the pic for easy referral.

Arjay

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Post subject: Re: Blackface bassman 1967 AB165
Posted: Tue Mar 06, 2012 7:30 pm
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Just how much are you guys gonna fuss if i only change the one with a hole in it ?

$20 a piece for 20uf 600 volt astrons ? Dang I'm not rich ya know.

here is a picture of my latest band member, My son is off playing guitar and bass on St Croix, yep in the virgin islands, he is doing a youth ministry internship down there so....
all of the sudden my daughter (Nelly) picks up her guitars and start going at it.
makes a dad so happy !!!!

Image

Image

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