Old resistor identification

[yorgle]

I picked up a sweet 1950’s Regal amp this weekend and got it up and running today.  It’s a SE with 6SC7 and 6SJ7 instrument/microphone preamp tubes, an unknown and unmarked driver tube, a 6v6 output and a 5y3 rectifier.  It had a nasty random static noise that I traced to a crumbling cathode resistor on the output tube— a gray cylinder shaped cement type marked only with:  K000LOHM.  The resistor measures open on my multimeter and I cannot find a schematic for this amp.  Any graybeards here familiar with this type of resistor ID code?

[sluckey]

Sprague KOOLOHM is a brand of resistor. A single 6V6 would probably be happy with a 470Ω or 500Ω 5 watt resistor.

https://www.ebay.com/itm/Sprague-Koolohm-Resistors-7-Watt-500-5-Tolerance-New-Quantity-Of-5/264778793536?hash=item3da60bc240:g:S2gAAOSwxNte-MxH

[Latole]

I fix few of these Canadian amps. They are more '60 area than '50
They are made by Pepco, Pine Eletronics or Lifco. Regal is just a name on the cab

They are good amp with few mods.

Can you post good picture of chassis ?
 
http://web.ncf.ca/ac151/

[yorgle]

It never occurred to me that KOOLOHM might be a brand name- I was way overthinking it to be something like K= multiplier, some zeros and "L" being the roman numeral 50, so .0050 x 1000= 5 ohms which made no sense for a cathode resistor on a 6v6.   

I had a 450r 10W in my pile so I stuck that in and it sounds awesome.  As usual, thanks for the education, folks.  Latole:  This one says "made in Chicago".  I'll post some pics tonight, but it looks identical to this one on Reverb:  https://reverb.com/item/33484693-regal-twin-palm-1954-1958-serviced-video-free-shipping-eu-uk-swiss?bk=eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiJjMGVmZjU0ZS1jMmMxLTRiNGMtOTdmOC1lZTAwNzZlODkyYzciLCJpYXQiOjE1OTgyNzk0NDUsInVzZXJfaWQiOiIiLCJzZXNzaW9uX2lkIjoiIiwiY29va2llX2lkIjoiZWMyNTMxMDctZmY2ZC00YTI2LTkyZTktMTAwMzBhNmQ5NDQ5IiwicHJvZHVjdF9pZCI6IjMzNDg0NjkzIiwic291cmNlIjoiTk9ORSJ9.dbVdrMMJCOPn8RlCj9oXklcFZtQS9MiveAn44_u0b0Y

[Latole]

You may be right, this amp do not look those Canadian made amps I talk about. And yes it look more '50 amp
It's made in Chicago.

[yorgle]

So far all I've done to it (aside from cleaning out bug and spider husks) is replace the filter multicap and the burned cathode resistor and I installed a grounded 3 prong power cord.  That's all I'm going to do for now unless some other problem arises after playing it a while. 

Eventually, I'll have to figure out what the center tube might be?  I made the mistake of using saliva to clean off the markings so I could see them better, but unfortunately my acid dragon spit wiped them clean off without the slightest trace.  I tried the freezer trick and also the face oil trick but still can't see anything. 

[Latole]

Check if the fuse is the right one to protect your amp

[yorgle]

Check if the fuse is the right one to protect your amp

Good point, I'll check that.  My initial thought was to re-cap the whole thing, but it's clear that this amp has never been touched and was probably shelved way back when that cathode resistor died.  So as long as it works, I want to keep it as original as possible.  I left the filter can in place- just cut the wires from it and ran them to three new caps inside the chassis.  I might try to hollow out the can and hide the new filter caps inside it. 

What is the general consensus on death caps?  Since I've added a grounded plug, should I still disconnect it?

[yorgle]

Here's my find as I brought it home...looks nasty, but the chassis actually cleaned up really nice. 

[Latole]

What is the general consensus on death caps?  Since I've added a grounded plug, should I still disconnect it?

Remove it.

 

[yorgle]

What is the general consensus on death caps?  Since I've added a grounded plug, should I still disconnect it?

Remove it.

Ok, and just to be sure, it's this guy here, right? 

[Latole]

What is the general consensus on death caps?  Since I've added a grounded plug, should I still disconnect it?

Remove it.

Ok, and just to be sure, it's this guy here, right?

 

1- How many "modern" amps use death cap ?  None
2- What is the use of death cap ? Google .......

https://robrobinette.com/Death_Cap_and_Ground_Switch.htm

I strongly recommend replacing all two wire power cords with three wire cords with a chassis ground. I also recommend disconnecting or removing all death caps because they can be an extreme shock hazard if a three prong power cord is plugged into an improperly grounded power receptacle.

[HotBluePlates]

It never occurred to me that KOOLOHM might be a brand name ...

A too-clever joke referring to Coulomb.

What is the general consensus on death caps?  Since I've added a grounded plug, should I still disconnect it?

1- How many "modern" amps use death cap ?  None
2- What is the use of death cap ? Google .......

https://robrobinette.com/Death_Cap_and_Ground_Switch.htm
...

Some amps today use IEC inlet EMI filters, which is the modern (and safe) version of the "death cap."

Anyone can implement a safe "death cap and ground switch" using a Class Y capacitor.  In fact, a lot of amps (and "surge protector power strips") might have Class X ("across the line" or Hot-to-Neutral) cap and/or Class Y ("line to ground") caps, but onlookers simply see "surge suppressor" and don't think further.

Done right, with the right safety-rated parts, they can reduce noise in the amp that's riding in on the power cord.

[tubeswell]

It never occurred to me that KOOLOHM might be a brand name ...

A too-clever joke referring to Coulomb.

How many cool ohms in a coulomb?


1 C = 1 A x 1 s or 1 F x 1 V  and 1 V = 1 A x 1 R and 1 F = 1 C / 1 V, so

=> 1 V / 1 R / 1 s  = 1 F x 1 A x 1 R

=> 1 V / 1 R / 1 s = 1 C / 1 V x 1 A x 1 R

=> 1 V / 1 R / 1 s = 1 C / (1 A x 1 R) x 1 A x 1 R

=> (1 A x 1 R) / 1 R/s  = 1 C / (1 A x 1 R) x 1 A x 1 R

=> (1 A x 1 R) / 1 R = [1 C / (1 A x 1 R) x 1 A x 1 R] x 1 s


=> 1 R = {[1 C / (1 A x 1 R) x 1 A x 1 R] x 1 s}/ (1 A x 1 R)


I think I got that right?       (I got a feeling something is staring me in the face, but probably too many photons hitting my eyeballs from staring at the computer screen)



Cool amp yorgle

[bmccowan]

That amp is too cool for school man. That chassis looks Valco. Their early amps had that type of chassis, they were made in Chicago, and Valco traded with Regal, using Regal bodies for some of their guitars. I wish you could still get those round faceplate control indicators.
That cabinet is like an old radio cabinet, amp will look spectacular if you can bring that back.
I always get rid of that cap, and install a 3 prong the same way the smart guys here do: Neutral to one of the PT leads; Line to the fuse first and then to the power switch; Safety ground to its own chassis connection.

[shooter]

 

I think I got that right? 

It's close enough for me


I'm doing P/V + gravity stuff in mental physics, I don't want to let the math in 

[Latole]

Some amps today use IEC inlet EMI filters, which is the modern (and safe) version of the "death cap."

 

To me, it is not a "death cap", a words use only in olds vintage amps.
And I did not look a "death cap"

[PRR]

It never occurred to me that KOOLOHM might be a brand name- ....

That "KOOL" krap is popular with resistor makers. Guy two peninsulas over from me sells these.

http://www.percyaudio.com/