Thanks for being a big help with my AK40 power supply questions. I read your responses and just want to make sure I understand you fully.
Can you provide me with a link to the AK40 power supply schematic. All of the drawings that I have of the power supply only show connection points and wire colors (no mention of capacitors (values and locations).
You mentioned that the AF & Detector bypass caps attached to the lower right two terminals of the power supply. I assume you mean 1 each. I can cut the leads to these two caps and replace them with the 10 microfarad caps you mentioned. Where do the other two ends of these 10 microfarad caps attach to?
Also I read that the 1st AF bypass and Detector bypass caps are rated at 0.5 microfarads. Won't replacing them with 10 microfarad (20X larger) caps cause a problem? You mentioned that I can use just audio bypass caps. Are these special types of caps?
You mentioned that there are 3 additional filter caps also located within the tar of the power supply. The common negative for these caps go to the mounting stud on the right. Is this mounting stud also buried in the tar? As I understand it this mounting stud is where each one end of each of the three caps is attached. I need to re-attach one end of each of my new 10 microfarad caps to this common negative mounting stud. Again, where do the other end of the three new caps attach to?
The original 3 caps are buried way down in the bucket under tar. If I snip these caps and then re-attach the new caps won't there be just a new cap and an old cap attached in series. I guess I don't understand.
The 100K and 12K resistors that are located just under the connection board of the power supply should be rated a 1 watt. Is that correct?
You mentioned a wire wound resistor with two sections also located under the connection board. I assume this two section wire wound resistor is located in the same vicinity of the 100K and 12K resisitors. I didn't understand what you meant by two sections. Is that like two resistors in one? Also what values should I be looking for in this two section wire wound resistor? If its bad, can I just replace it with a new standard resistor of a certain type?
Finally, I have a question concerning the set of three capacitors (located in a playing card sized canistor (with tar) mounted on the radio chassis just under the third #26 vacuum tube. A diagram shows that these RF filament and Plate circuit by-pass caps are connected in parallel and then grounded to the chassis. If I replace these caps should I use one 0.3 microfarad (R-F filament bypass)cap and two 0.05 microfarad (R-F plate bypass caps in their place?
Thats all for now. Thanks again for your help, and sorry for the lengthy list of questions.
There are schematics here on nostalgiaair. Here is one. Your supply doesn't have the regulating resistor in AC primary and has 2 chokes instead of speaker field.
http://ww3.nostalgiaair.org/schematics/A-K/A-K_3-16.gif
Value of audio bypass caps aren't critical. Any type cap will do. .5 mfd would be ok if you have them but 10 mfd will also work. They connect to B+ and do not effect signal quality. One each, attaches to the lower two terminals on the connecting board. The opposite end of the far right cap connects to ground. Ground is the two mounting studs for your connecting board. Opposite end of second from right connects to second from left terminal on bottom. You can find parts layouts here on nostalgiaair.
Mounting studs are the threaded ones which hold your connecting board. These are the grounds. All you need to do is remove one end of each cap to disconnect it from the circuit. Filter cap replacements connect between a mounting stud and wires going over partitions in your supply.
The AF & Detector resistors are under the lower board, right above the tar. Use 1 watt resistors. Your wire wound resistor is on top of the lower board. Yes, it's two resistors in one. One section will be around 2K to bias a 71A and the other 650 ohms for 26 bias. These values may not be exact but are close.
The two filament bypass caps should be ok on your radio chassis. There is very low voltage across them. Even if leaky won't cause a problem. I normally use 1 mfd for plate bypass cap but just about any value will work (.1 mfd - 10 mfd). B+ voltage is across this one and it should be replaced.
Once you get into the power supply this should make sense.
Norm
: Norm:
: Thanks for being a big help with my AK40 power supply questions. I read your responses and just want to make sure I understand you fully.
: Can you provide me with a link to the AK40 power supply schematic. All of the drawings that I have of the power supply only show connection points and wire colors (no mention of capacitors (values and locations).
: You mentioned that the AF & Detector bypass caps attached to the lower right two terminals of the power supply. I assume you mean 1 each. I can cut the leads to these two caps and replace them with the 10 microfarad caps you mentioned. Where do the other two ends of these 10 microfarad caps attach to?
: Also I read that the 1st AF bypass and Detector bypass caps are rated at 0.5 microfarads. Won't replacing them with 10 microfarad (20X larger) caps cause a problem? You mentioned that I can use just audio bypass caps. Are these special types of caps?
: You mentioned that there are 3 additional filter caps also located within the tar of the power supply. The common negative for these caps go to the mounting stud on the right. Is this mounting stud also buried in the tar? As I understand it this mounting stud is where each one end of each of the three caps is attached. I need to re-attach one end of each of my new 10 microfarad caps to this common negative mounting stud. Again, where do the other end of the three new caps attach to?
: The original 3 caps are buried way down in the bucket under tar. If I snip these caps and then re-attach the new caps won't there be just a new cap and an old cap attached in series. I guess I don't understand.
: The 100K and 12K resistors that are located just under the connection board of the power supply should be rated a 1 watt. Is that correct?
: You mentioned a wire wound resistor with two sections also located under the connection board. I assume this two section wire wound resistor is located in the same vicinity of the 100K and 12K resisitors. I didn't understand what you meant by two sections. Is that like two resistors in one? Also what values should I be looking for in this two section wire wound resistor? If its bad, can I just replace it with a new standard resistor of a certain type?
: Finally, I have a question concerning the set of three capacitors (located in a playing card sized canistor (with tar) mounted on the radio chassis just under the third #26 vacuum tube. A diagram shows that these RF filament and Plate circuit by-pass caps are connected in parallel and then grounded to the chassis. If I replace these caps should I use one 0.3 microfarad (R-F filament bypass)cap and two 0.05 microfarad (R-F plate bypass caps in their place?
: Thats all for now. Thanks again for your help, and sorry for the lengthy list of questions.