Motorboat arrived at pier M3 and then sank

**gtc** · 08-10-2012, 04:28 PM

And another zapping vid here:

http://www.youtube.com/watch?v=apPSbHqmYIU

**Tdawg** · 08-10-2012, 07:30 PM

Ahh yes... I have seen those videos somewhere before.... Thanks for posting though, I appreciate it. I'd like to think I can handle the zapping process, but who knows.. my electrical experience consists of replacing batteries in my kid's toys. Guess you gotta start somewhere.

I'm more confused with all the different types of caps and which ones to use....

**gtc** · 08-11-2012, 04:17 AM

Originally Posted by Tdawg

Pretty sure mine is a 1957..... hoping to move it out this weekend and take a look at what's going on back there. I have no idea where to start.....are new caps fairly inexpensive? Not sure what type I would need and the best place to get them...

As mentioned above, the electrolytic capacitors are the ones that tend to give most trouble. The electrolyte is a paste that dries out over time and with heat and eventually the cap is way out of spec and sometimes the internals will short out causing a big fizz or an explosion of varying ferocity. Such explosions tend to occur on old gear that hasn't been powered up for a long time. I don't trust 40 year old electros and I replace them on principle (note that electros made these days will not last anything like 40 years). The ones involved here run to a few dollars each. Get them at Mouser, etc, or from a Hammond resto supplier where you'll probably pay a little above par but you are likely to be sent the correct parts if you've given them the correct model details.

One complication that can arise is that some are canned multi-section electros, that is, there is more than one capacitor in the can. Oftentimes you can't find a replacement today so it's a case of either re-stuffing the cans with modern caps (not an easy task for the uninitiated), or soldering new caps under the chassis after disconnecting the existing cans which are left on the chassis for the sake of cosmetic completeness.

Electrolytic capacitors are polarized. That is they have positive and negative electrodes. They must be installed with the polarity the right way around or you'll experience the "fizz/bang!".

The other capacitors, if original, are usually "paper" types (paper dielectric with a wax outer case). These also drift off spec over time but don't usually go "bang!" like the big electros. The majority of non-electro caps are in the tonewheel and they were (allegedly) specially selected at the factory to closely match the associated coil. You can buy replacement kits for those but there is much debate on the worth of (a) the kits and (b) replacing the whole set. Plus it's a lot of work and really ought to involve a re-tune from one end to the other at completion.

**indianajo** · 08-11-2012, 04:43 AM

AS much as I harp about the dangers of > 20 year old electrolytic caps, motorboating is more likely to be paper caps on the plate or grids of the tubes. On the vibrato tube, of course, since that is the only function where you are getting it. Grid and plate caps wear out too, just not as surely as rubber sealed electrolytics.
Caps have two numbers, size (mf up to 1980, now called uf) and Working voltage. You need the same or a little higher. The electrolytics have a plus on one end or squares, circles, triangles on tall cans. More details on how to buy and safely replace them, look at this thread:http://www.diyaudio.com/forums/tubes...ube-amp-3.html
The plates of the tubes look like T's on the print, the grids look like dotted lines. The numbers on the schematic correspond to the numbers molded in the bottom of the tube sockets. Use a lot of light. measure all metal at under 25 VDC before touching it, don't work alone, don't talk around high voltage. Wear safety glasses, solder splashes.

**Tdawg** · 08-12-2012, 08:33 PM

Originally Posted by gtc

As mentioned above, the electrolytic capacitors are the ones that tend to give most trouble. The electrolyte is a paste that dries out over time and with heat and eventually the cap is way out of spec and sometimes the internals will short out causing a big fizz or an explosion of varying ferocity. Such explosions tend to occur on old gear that hasn't been powered up for a long time. I don't trust 40 year old electros and I replace them on principle (note that electros made these days will not last anything like 40 years). The ones involved here run to a few dollars each. Get them at Mouser, etc, or from a Hammond resto supplier where you'll probably pay a little above par but you are likely to be sent the correct parts if you've given them the correct model details.

One complication that can arise is that some are canned multi-section electros, that is, there is more than one capacitor in the can. Oftentimes you can't find a replacement today so it's a case of either re-stuffing the cans with modern caps (not an easy task for the uninitiated), or soldering new caps under the chassis after disconnecting the existing cans which are left on the chassis for the sake of cosmetic completeness.

Electrolytic capacitors are polarized. That is they have positive and negative electrodes. They must be installed with the polarity the right way around or you'll experience the "fizz/bang!".

The other capacitors, if original, are usually "paper" types (paper dielectric with a wax outer case). These also drift off spec over time but don't usually go "bang!" like the big electros. The majority of non-electro caps are in the tonewheel and they were (allegedly) specially selected at the factory to closely match the associated coil. You can buy replacement kits for those but there is much debate on the worth of (a) the kits and (b) replacing the whole set. Plus it's a lot of work and really ought to involve a re-tune from one end to the other at completion.

Thanks so much for taking the time to explain that to me.... The fewer things I have to fix, the better at the moment (or at least until I'm more comfortable) ...I'm still confused on the different types of electrolytic caps..... after looking at mouser and reading other threads.. I see aluminum, poly, ceramic, etc... is there a specific type to use or is it just personal preference? I took a look at some of the kits from organ sites too....I suppose that would make it easier for someone like me...even if it does cost more. Thanks again for the help!

Originally Posted by indianajo

AS much as I harp about the dangers of > 20 year old electrolytic caps, motorboating is more likely to be paper caps on the plate or grids of the tubes. On the vibrato tube, of course, since that is the only function where you are getting it. Grid and plate caps wear out too, just not as surely as rubber sealed electrolytics.
Caps have two numbers, size (mf up to 1980, now called uf) and Working voltage. You need the same or a little higher. The electrolytics have a plus on one end or squares, circles, triangles on tall cans. More details on how to buy and safely replace them, look at this thread:http://www.diyaudio.com/forums/tubes...ube-amp-3.html
The plates of the tubes look like T's on the print, the grids look like dotted lines. The numbers on the schematic correspond to the numbers molded in the bottom of the tube sockets. Use a lot of light. measure all metal at under 25 VDC before touching it, don't work alone, don't talk around high voltage. Wear safety glasses, solder splashes.

Thanks for the tips and the explanation, Jo.... Thanks for the link as well. I have to say, I was already a little paranoid about messing around with this stuff, but after reading some of the "stickys" on that forum regarding newbies working around high voltages, now I REALLY am paranoid. I plan on studying up as much as I can...and taking my time. Hoping my Dad can help me out as well. Thanks again for the help!