Do I need to remove the tar from my AK44 and replace the capacitors before I plug the set in or can I test them in their current state? Hard to image 80 year old caps being any good. Are there other hidden parts I should check before I fire it up? Thanks.

:Do I need to remove the tar from my AK44 and replace the capacitors before I plug the set in or can I test them in their current state? Hard to image 80 year old caps being any good. Are there other hidden parts I should check before I fire it up? Thanks.
Hi Robert
I have an AK55C, I know what your talking about, capacitors and other key components are sealed in metal cans with a very hard tar like substance, to be honest, I went through the chassis and only replaced what I could see and get out, I never attempted to break open the numerous sealed cans.
Mark

It is wise to replace all capacitors. If you are having trouble removing the tar, soak the can in gasoline. Another method is to heat the can in an oven. This stinks, though. It is best done in a charcoal or gas grill.

I had thought of another idea. Dont know if its possible, but if small replacement caps are available, can the "tar can" be left alone and caps be hidden somewhere else? That would keep the original look.

Robert's idea will work, and the replacement caps may fit in the original can, between the lid and the tar. You can fish out the leads from the original caps as they exit the tar.

The original filter caps were non-polarized paper caps, which is why they take up a lot of room, even though they are small in values. You will replace them with electrolytic caps, so watch the polarity.

The original caps may be leaky, but not as bad as old electrolytics. You can try bringing up the set slowly on a variac, and see if the original caps are OK. I have several AK metal-case sets running fine on the original filter caps. However, replacing the caps is always a good idea.

:I had thought of another idea. Dont know if its possible, but if small replacement caps are available, can the "tar can" be left alone and caps be hidden somewhere else? That would keep the original look.

Doug, why do I need to replace the original non-polarized with polarized? Non-polar caps are plentiful. I was thinking about locating the new caps somewhere else other then inside can. I would like to be able to open the can and have it look like it did 80 years ago.

Robert: You can use film caps, but they will be physically much larger and somewhat more expensive than electrolytic caps. If you're intending to put the replacements under the chassis, the clearances may be tight using film caps.

Here's Leigh's modern schematic for your set: http://www.atwaterkent.info/TechData/Drawings/Images/AK09900sch.pdf

There are three original filter caps: two @ 1uF and one @ 1.5uF. Might want to put replace with two @ 2uF and one @ 4uF.

If the Model 44 is like the others that I've worked on, the filter caps are in one compartment of the power unit, and the two chokes are in the other.

:Doug, why do I need to replace the original non-polarized with polarized? Non-polar caps are plentiful. I was thinking about locating the new caps somewhere else other then inside can. I would like to be able to open the can and have it look like it did 80 years ago.

You can put something in place of the tar once you're finished. If you melt the tar out, just save it and put it back in. If not, locate something else that'll look like tar. You can even use parafin and black crayons as long as the can isn't near anything hot. If you want an original look, melt the tar out. Put in the new caps and attach them to the old wires. Then put in some black wax and you're finished.

T.

:It is wise to replace all capacitors. If you are having trouble removing the tar, soak the can in gasoline. Another method is to heat the can in an oven. This stinks, though. It is best done in a charcoal or gas grill.

Guys,

I have had pretty good luck using an infrared heat lamp with hood. I remove the bathtub cap and place it on a couple of 1/2-inch bolts tar side down and aim the lamp close to it. The tar runs out and then I remove the old cap and clean the tub with solvent. Then replace the cap with a new one inside the tub and seal it up. I can do this under the carport.

Radiodoc

Doc, what do you catch the molten tar in? Then, do you remelt it to seal the new caps?

I wonder if there is something that mimics tar, but not as nasty - maybe black silicon caulk? - that could be used to seal the replacement caps.

The last time I got involved in this messy process was to replace a choke that had opened. I didn't replace the tar with anything, figuring eventually somebody may need to get at the replacement components.

:
:Guys,
:
:I have had pretty good luck using an infrared heat lamp with hood. I remove the bathtub cap and place it on a couple of 1/2-inch bolts tar side down and aim the lamp close to it. The tar runs out and then I remove the old cap and clean the tub with solvent. Then replace the cap with a new one inside the tub and seal it up. I can do this under the carport.
:
:Radiodoc
:

The tar isn't necessary, except as mechanical support. Originally it kept the moisture out (for a little while) and it was readily available and cheap (there are oil refineries just south of Philadelphia).

Doug,

I don't generally put the tar back in the bathtub caps. I use liquid plastic (which can be found in the paint section of the hardware)to mount the new cap inside. However, I did remove the tar from a Crosley GemBox power supply choke recently (one of the leads was shorted to the case). I collected the tar in a clean tuna can. After replacing the insulation on the choke leads, I used a small torch to heat the tar in the tuna can and poured it back in the choke case. I generally collect the tar from the bathtubs on a piece of aluminum foil and dispose of the tar and foil. I use a fire brick to sit everything on. I suppose one could use a large tuna can to collect the tar from a larger transformer or choke if the tar was to be reused.

Radiodoc

:Doc, what do you catch the molten tar in? Then, do you remelt it to seal the new caps?
:
:I wonder if there is something that mimics tar, but not as nasty - maybe black silicon caulk? - that could be used to seal the replacement caps.
:
:The last time I got involved in this messy process was to replace a choke that had opened. I didn't replace the tar with anything, figuring eventually somebody may need to get at the replacement components.
:
::
::Guys,
::
::I have had pretty good luck using an infrared heat lamp with hood. I remove the bathtub cap and place it on a couple of 1/2-inch bolts tar side down and aim the lamp close to it. The tar runs out and then I remove the old cap and clean the tub with solvent. Then replace the cap with a new one inside the tub and seal it up. I can do this under the carport.
::
::Radiodoc
::

Use black wax if it's not near hot items. Mix black crayons with parafin. I've done it before and it looks quite nice.

T.

Hi Robert

Sorry I didn't see your posting earlier. There is an easier way to replace capacitors in an AK 44 power supply.

The power supply is built in 3 sections. Each section is separated by metal. Wires from each section go over these pieces of metal. The first section on the left is power transformer. Other two contain chokes and capacitors.

You can soften tar on top of the power supply with a heat gun or hair dryer. Use a screw driver to remove tar which covers connecting wires. Use a meter with pin for probe to identify wires. You can cut these wires and replace caps with 10 mf @ 450 volt electrolytics. They are small and will fit under the connecting board.

Two caps, 1st audio and detector, can be removed by cutting wires going into the tar. Replace them on the side of the board. Also two carbon resistors will be found under the board. Both will be high in value and should be replaced. The flat wire wound resistor has two sections. As long as not open it's good.

Norm

:Do I need to remove the tar from my AK44 and replace the capacitors before I plug the set in or can I test them in their current state? Hard to image 80 year old caps being any good. Are there other hidden parts I should check before I fire it up? Thanks.

Norm, I looked on both the new and old schematics and dont see 10mfd caps, only 1mfd caps in the power section. Did you increase these in your set? What are those big black round cylinders in the right side of the set?

Robert: Norm is suggesting that the filter caps be upsized from their original values.

The two cans hold audio interstage transformers. Check the primary and secondary windings of each to see if they are open - a common problem. If they are not open, leave them be.

:Norm, I looked on both the new and old schematics and dont see 10mfd caps, only 1mfd caps in the power section. Did you increase these in your set? What are those big black round cylinders in the right side of the set?

I started to use a propane torch on the outside of the power supply to remove the tar. What a major mess. But I was wondering is there any thing I can damage, ie the power transformer, by using a torch on the outside of the unit?

Robert,
Regardless of the many suggestions posted, I've successfully dismantled/replaced canned condensers and saved contents for posterity. I have a MS Word document describing my process, pit falls, safety issues etc. If interested contact my email.

marv

:I started to use a propane torch on the outside of the power supply to remove the tar. What a major mess. But I was wondering is there any thing I can damage, ie the power transformer, by using a torch on the outside of the unit?