Value of this Cement Power resistor please?

[Jerry2013]

I stupidly broke off this thing from one of my amps. Its a big 1 and 7/8" sand resistor, and I need to find another one. its 8000 Ohm cement resistor, but I dont know what watt. I bought a different 8000 ohm, but it was much smaller probably not the right wattage value. This comes form an Alamo Fury amp, of which there are no schematics that I know of , and which I'll probably take to a tech.;

[IMG:800:600]http://i111.photobucket.com/albums/n134/dickdog1/003-1_zps29c9c8f3.jpg[/img]

And here is the 8K 7 watt I bought, but its much smaller, only an inch and 3/8's. Yeah, I'm not basing the replacement on size, just bought it thinking itd be the right one, but wouldn't have used it till 100% confirmed. I bought 25 of these littel cement 8K 7W resitors(D'oh), and will keep a few in case, but if anyone wants the rest gratis, PM me.;

[IMG:800:600]http://i111.photobucket.com/albums/n134/dickdog1/004-1_zpsf9167f96.jpg[/img]

Pesented for your viewing pleasure; one Alamo Fury vintage tube guitar Amplifier-


[IMG:800:600]http://i111.photobucket.com/albums/n134/dickdog1/003-1_zps59ab21c6.jpg[/img]

There is already a three prong cord on the amp (phew!). Should I put grid screen resistors on the output tubes? Ik 5W wirewound cement resistors soldered from pin #4 to Pin #6, correct?

[IMG:800:600]http://i111.photobucket.com/albums/n134/dickdog1/002-2_zpseb7936ed.jpg[/img]

What are these Green caps? They are 0.047 @ 50V. Are they any good ? Should they be left in, or should I have them replaced with tropical Fish? I know that one big Brown Turd Drop cap has got to go, right?, as they are pretty much dogs as everyone seems to think.

[IMG:800:600]http://i111.photobucket.com/albums/n134/dickdog1/001-2_zps8084d214.jpg[/img]

( Why am I up at 3 am CST? I'm an Insomaniac. I never do any amp wprk when I am fatigued, I'm taking this stuff dead seriously)

[alvarezh]

Hi, good morning!

The original resistor is probably 10 watts, that's why yours is smaller. Go for a 10 if you can buy just one, no need to buy 25, unless you want to start a charity.

Old amps have worked well without the screen resistors. Have not seen the schem, but if it uses 6V6s or 6L6s then you're good to go with 470 ohms 5W. 1K won't hurt dough. IMPORTANT! you have to desolder the lead into pin 4 and solder it to pin 6, then install the resistor from pin 6 to pin 4, again assuming the above mentioned tube types.

I would leave those caps in for now, they are tone caps and there is a good chance they are OK. I would replace all the electrolytics on the power section and the cathodes before firing it.

Once you test the amp, then you can start doing the tone cap changes to taste.

Again, good morning!

[martin manning]

Pin 6 is often used as a tie point for screen resistors on 6L6 and 6V6-type tubes because there is no internal connection. Here we don't know what the tube type is, and it looks like pin 6 is already in use anyway. We don't even know if pin 4 is the screen.

You said you will probably take this amp to a tech, but then you are fishing for information on how to modify it yourself. Why are you trying to "fix up" your amps? If you are wanting to sell them (I see you have listed a couple of items for sale here) then you are probably losing money. I would much rather buy an amp in original condition in need of some work than one that has been f'ed up by some amateur.

[Jerry2013]

Pin 6 is often used as a tie point for screen resistors on 6L6 and 6V6-type tubes because there is no internal connection. Here we don't know what the tube type is, and it looks like pin 6 is already in use anyway. We don't even know if pin 4 is the screen.

You said you will probably take this amp to a tech, but then you are fishing for information on how to modify it yourself. Why are you trying to "fix up" your amps? If you are wanting to sell them (I see you have listed a couple of items for sale here) then you are probably losing money. I would much rather buy an amp in original condition in need of some work than one that has been f'ed up by some amateur.

Hi. I appreciate your taking an interest in this thread. Theres really not much to be done to the Fury. Its an easy recap, I'm just stuck on the value of the Cement resistor I asked about. Would you concur its a 10 watt resistor I need? If I'm not mistaken , I can go up in value on the wattage a certain percentage, as a rule of thumb?
I may sell the Fury, and I may sell the Traynor Bassmaster , depending on how it sounds. I'm also considering however having THE Dave Friedman modify the Traynor Bassmaster nto a hot Rod Marshall amp, as he said he could do a cool dirty thing with it, and I assume thats what he meant, but need to talk with him again.

I'll most likely keep the little Traynor Bassmate as a practice amp- again, very simple recap, and already had 3 prong cord.
All of these amps , even the Bassmaster are fairly straightforward, and many examples of cap jobs on them are done basically the way I am going to be doing it hopefully, since the big can caps aren't practical to replace and all the big paper Electrolytic Caps were basically just sitting there in clamps ,, and I do intend to put them on some kind of amp board and silicone the board and caps down so it won't vibrate and its safe and looks neat.

About the tech, I said I would probably take the amp in, depending on if I decide to put the screen grid resistors in it, which I most likely will not not, I was just trying to see what it entails and how involved it would be.

I can do this stuff, and do it properly ( and properly in this instance means adequately) . I have no doubt whatsoever I can do this or I wouldn't be trying it. Will it be 'mil-spec'...no, and I can appreciate how some of you feel that is the only way to operate, and thats cool, its great, and I'd love to be able to do it or have it done that way , but it *can be done safely and properly and look good just using average common sense and general practical aptitude.

I'm stuck on the cord thing for the Bassmaster, but I can study and get it done right. I'm also wanting screen grid caps on the Bassmaster, and will be asking about that. I'm far from the first one doing this who wasn't exactly certain how.
I agree that coming here without knowing how to do a 3 prong cord was a preposterous thing to do among such highly qualified and experienced experts, and I regret how I manged that. On the other hand ,sure, just cause I can take it to an amp tech does not beyond a doubt mean the amp would be fixed properly anyway, trust me on that.
There are many many instances , just read, where people don't know who to take their amps into, and end up having their job botched by a supposed expert.
I happen to know what is most likely an excellent tech now though, although I've been to my share of losers in the past.
Anyway, I'm not harping on you or any of you at all man, again, I truly appreciate your interest, and do you know about that cement resistor?

BTW, the tubes are 7868's in the Fury, thanks guys.

[Cantplay]

Mount the resistor better.

I see the resistor bypassed with a cap, and wires just twisted together. Begging to short to ground if inertia has its way.


All that unsupported weight with long leads caused it to fail.

John

[Leo_Gnardo]

WOW Jerry that Fury looks like it could have some possibilities. First of all I was worried a couple days ago that it was one of those cheapo "hot chassis" specials. Not so! Beefy PT, a choke, and an OT that supports 7868. Already has grounded cable. So far so GOOD.

Briefly, those blue-green caps are the equivalent of tropical fish, and not anything to write home about. I sometimes find a leaker. First place you want to check for a baddie is on the feed to the output tubes' control grids. Also don't worry about the brown "lumpy" cap. Maybe it's not "fashionable" but as long as it's functioning don't sweat it. For good working currently made caps think Mallory150 mylars. I use 'em, they have a good clear tone, not expensive. Also Xicon metallized polypro have proven themselves quite acceptable.

Your 7868 output tubes are equivalent to 7591, just have different bases. If they're still working & more or less balanced, again no sweat.

Sort those resistors out & we'll help you thru the rest of it.

[MCK]

Here's an idea... Since you have 25 of the 7W resistors... Why not wire 2 in parallel to each other getting a 4K 14W unit. Then do it again getting another 4K 14W unit. Then wire these two units in series... You will end up with a neat 8K 14W monster! You can actually put them all together and wrap with some wire to hold together. Cable tie comes to mind but it might melt or go brittle over time. Just an idea. Best of luck!

[rdjones]

BTW, the tubes are 7868's in the Fury, thanks guys.

[img:150:164]http://www.nj7p.org/Common/Tube/SQL/Bases/9NZ.png[/img]
http://www.nj7p.org/Common/Tube/SQL/Tub ... ?Type=7868

[hakantoz]

MCK, has given good solution of using available parts. Another option is to compare resistor mechanical dimension with below chart, if the dimension match with CB15, MCB15 then it is 15W resistor. I found this information from digikey by sorting the wirewound resistors (CB/MCB Series Ceramic Housed with Axial Leads Wirewound Resistor).

[img:660:344]http://i.imgur.com/D2Wq8ec.png[/img]

[Jerry2013]

thanks! If the original was 10watt ,Would it hurt to step up to a 15 watt resitor( 8000 ohm) to be safe? Actually, I have a 8000 ohm 20 watt, can i yuse that instead of the 8000 ohm 10 or 15 watt, meaning is it okay to step up that much in wattage?

[jelle]

Yes, is ok.

[Jerry2013]

You guys are the best-no, the best of the best. Thanks again.