Leslie amp resistors

[Aback22]

Could anyone help me identify the resistors in my Baldwin-Leslie power amp? Been working on figuring it out and replacing old components. Have had some shock hazards. Can't seem to find an exact schematic for the one I have. Any help would be greatly appreciated.

[David Anderson]

I thought I posted a schematic about 10 days ago.

I'm not sure what you mean by identifying the resistors. I see a mix of carbon composition and wirewound resistors.

[skydawg]

Resistor values are encoded in the colored bands.If you google "Resistor Values" or similar,you`ll get the info needed to id most of them..It`s not difficult to learn.

[Aback22]

Thanks guys. Yes you did post a schematic, but I'm having trouble locating where the 5.6 ohm 10% resistor is on there. It connects to the smaller of the filter caps (far right side in the picture). Skydawg, thanks and yes I did find that color band code online which is very helpful. However, how do you know how many watts the resistor is? The one in question is green, blue, gold, silver-- as identified above. But how many watts? This one blew up and smoked last time I turned on the amp! So it needs to be replaced. It's 1 3/4" long.

[Jyvoipabo]

Good evening,

I think the big black cylinders with colored bands are Sprague Bumble Bee capacitors. Not resistors.
Drop 'sprague bumble bee' in Ebay you will be surprised.
If that's right, you have to replace all of them.

JP

[Drawbar Dave]

This is a great help for identifying resistor values that I use http://www.csgnetwork.com/resistcolcalc.html

[skydawg]

There are no power rating codes on carbon comp resistors,you`ll be ok with replacing with the same resistance value.A 1 3/4" resistor is probably a wire wound.These usually have a power(watt) rating printed on the body.

[Aback22]

I see, those large ones are Bumble Bee capacitors. Is there a more efficient modern replacement I can put in? Is it correct to identify this one as .22uf 400v? Also the resistor that blew was 5.6 ohm 10%, but I can't find those at 5w. Is it okay if I go with a 5% tolerance one?

[Aback22]

The busted resistor. Thanks for all the help guys, I'm new to this..

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Confusing. For example, your schematic shows .47uf caps that I don't see anywhere in my amp. Also, just practically when I zoom in to try to see the values they get blurry. Maybe I'm misunderstanding something? Thanks.

- - - Updated - - -

[David Anderson]

The reality of schematics is that they don't always exactly match the circuit as found. They were intended to be used by technicians who have some level of basic understanding of the circuits and who are, thus, able to understand why a certain component might be missing or why an extra component appears that's not on the schematic. There were always running changes in production. Some companies were careful about documenting them, but others were not.

It's surprising, for example, to find any Gibson guitar amp that precisely matches the schematic, and for my early Farfisa Compact Duo, no complete schematic exists at all.

You're trying to learn the rudiments of vintage electronic repair on an amp that's neither very common or well-documented. I've been working on Hammonds and Leslies since 1990, and I've only seen one BL-1 in that entire time. I didn't even know they existed before I saved it from the trash. I'm sorry if you wanted a better schematic. That's all I have.

[Aback22]

You're right David, I've never really looked into electrical circuitry until taking apart this vintage amp. I'm in "101 class" and asking a lot of questions. You've been more than helpful. I just wanted you to know why I still had questions, even after your schematic.

[Aback22]

One last question-- when the hot/live wire comes in, does it go through that fuse or does it go straight over to the Power Transformer? Then the common wire will do whichever the hot wire is not doing.

[Jyvoipabo]

Hello,

In my opinion, the capacitors you identified are in parallel, and serve as a mains filter. That is 0μ22 x 2 = 0μ44
In such a case, you can easily replace it with one MKP 0μ47 275V X2

The other 2 capacitors are link capacitors that you can replace by film capacitors 0μ1 630V.
If you have a meter, measure their value. You will be surprised again.
May be this capacitors are not innocents in the burning of the resistor.

JP

[David Anderson]

I agree with Jyvoipabo. Where a 0.47uF cap is indicated on the schematic, there are two 0.22uF capacitors in parallel, probably because there wasn't a 0.47uF cap available. (That was a rather large value for a paper capacitor at the time.)

On the schematic, it shows a 5.0Ω 5W wirewound resistor, and that looks like the one that opened up. In reality, it appears to have been a 5.6Ω resistor, which was probably a more readily available value and close enough. If one of those 0.22uF bumblebee style capacitors is shorted, which is likely, that could burn up that resistor.

The other bumblebee style caps in the amp are 0.1uF. For those, I recommend Mojotone's Mojo Dijon. (Yes, the name is pretentious, but they are very good.) Replacing those will prevent burning up output tubes.

JP refers to an "X2" capacitor, which is a type of safety capacitor used in cases where, if it fails, it should fail open. These are now used for specific AC line filtering purposes and were not available back in 1959.

Here's an X2 cap in an axial package that might fit better than the more common radial types, more expensive because axial, but it's worth it sometimes to have it fit neatly on the original terminal strip.

https://www.mouser.com/ProductDetail...egLyPRqg%3d%3d

And it's time to replace all the electrolytic capacitors as well while you're in there. That would include the two 40uF high voltage filters, the 100uF/50V cathode bypass, and the 1000uF/25V brake circuit filter.

But none of these common maintenance items necessarily explains why you've been getting shocked.

[Aback22]

Sounds like a good list of components I can update on this amp. This also helps bring some clarity to the discrepancies on the schematic. One last thing: since I am using this for guitar I have separated out the wires coming through the 6 prong plug. The audio are connected to a 1/4" input I installed. The lead for the 12vdc motor is capped (not using that). I'm installing a 3-prong cord with the green grounded to the chassis. What I need to know yet is if the hot wire coming in should go to the path through the fuse or if it should go over to the power transformer?