The on-off switch? I tried a .01 cap there awhile back at the advice of another forum member, and it didn't stop it.

You can still hear the pop after disconnecting the audio from the tuner to the power amplifier. I think it has to be in the power amplifier somewhere.

Larry, try removing the rectifier tube and then turn the set on and off. If it still produces the click, then it is probably induction from the power transformer directly into the output transformer, and there is nothing to do about that short of separating them.

-David

As I said earlier, troubleshooting this set has been a real learning experience for me. I didn't know until this past weekend that if you have a bad picafared (pF) cap, you can use a microfared value cap in its place. I always thought if you had a bad pF cap that you'd have to order a pF replacement. I needed a 4700 pF cap in the tuner, and a buddy of mine told me about this corresponding chart which shows that a .0047 microfared cap can be used in its place...it's the same thing. As Johnny Carson used to say, "I did not know that."

Here's a capacitor conversion chart which shows what you can use. I suggest all members save this in their favorites for future reference.

http://www.justradios.com/uFnFpF.html

Also, here's a color coded resistor chart which I use regularly to replace resistors. You can replace them just by the color codes on the resistors you're replacing, and you don't have to even look at the schematic.

http://samengstrom.com/24614782/en/read ... olor_Codes

David, there is no noise whatsoever with the rectifier tube pulled.

It's not as simple and cleancut as that....

I don't fully rely on the actual resistor bands, I rely more on the schematic, because some banding does change color over time or due to heat.
An orange band can turn yellow, or even a reddish.
Blue can turn purple or even green.

Also...
Relying on learned theory, something most on here are oblivious to.....

Knowing the usual circuit design of say a 12AX7 tube, I know from experience that the plate feed of 250 volts would use NOT be a 4.7/47K resistor, more like 470K.

I intentionally threw what you underlined in there to see what you guys would say. I knew you, David or Doug would come back on me on that one. I always verify it is the correct value before installing it. I sometimes use the schematic, but more often than not I use the photograph of the resistors underneath the chassis in the Photofact, and determine the value by the parts list. Then, if the resistor color chart comes up with the same value, you're good to go.

You are right, some of the resistors are faded and difficult to tell color on some of them. However, on resistors that look brand new, they're usually correct color codes.

I realized last night that there's another .1 yellow cap going from the other 6AU6 tube to the 12AU7. There's also two .047 yellow caps that link the two driver tubes with the output tubes. I'm going to pull the amp today and replace those yellow caps with good Mallory white caps.

I simply don't trust these cheap yellow Chinese caps anymore, particularly in high voltage applications like this big power amp.

Wow...oh wow... oh wow... I just replaced all the yellow caps in the power amplifier with the white Mallorys from AES and the sound has come to life... sizzling..... I can't believe the difference a good quality cap makes over cheapo Chinese caps..... Think the .1 white Mallorys are $1.16 each at AES, but they're darned worth every penny of it.... Guess that'll teach me not to use 25 cent Chinese caps in a powerful amplifier. You get what you pay for, even with capacitors. It's a mistake to pinch pennies here.

Oh, and the speaker pop when turning the set on is gone also!!!!

SPLENDID!!!!!

While we're on the subject, how does the quality of "orange drops" compare to those yellow ETR caps?, from you guys with experience.

I'm sure the orange drops are much better quality caps than the yellow ETR's. I don't like them because they're much larger and, I prefer an axial lead cap over a radial lead, but they're excellent caps.

The truth is, these yellow ETR caps are junk, and I've proved it with this restoration.

I agree on the orange drops. They're large and they're not cheap, but I've never had a bad one.

-David

Are you saying this because the yellow caps are defective, or do you think that you can hear the difference between the Mallorys and non-defective Chinese caps?

Both!!! One of the yellow .1s was shorted and it was causing distortion in all modes...AM, FM, phono and tape. I replaced that one and the sound was wonderful on both FM and AM; however, on phono and tape, I couldn't turn the volume level up past half-way without getting distortion. The white Mallory caps eliminated both problems, and the Mark I now sounds un-freeking believable!!!! It now sounds like a $1600 set back in 1956 is supposed to sound !!!

There is a sound quality difference between brands of capacitors. I've heard the difference with my own two ears!!!!!

Brain...are you stirring the pot?

I've got yellow capacitors in my SHF-2 but the .1uf output coupling caps are not marked ETR. I've run a 1kHz sine wave into it with an 8-ohm resistive load and a Tektronix 453A dual trace scope on the output. I moved the 6V6's around so that it clips (clips off the top and bottom of the sign wave) fairly evenly at maximum undistorted output. I adjust the function generator output so that the output sign wave is just below clipping and counting the divisions on the scope scale I've got just over 13-volts AC into an 8-onm load. That's almost 22 watts output. My test equipment has not been calibrated in 30 years so take that into consideration. Being fairly familiar with how an amplifier of this caliber is supposed to perform, I'm good to go with the yellow.
However I'm going to keep a suspicious eye on them.

This thread is proof that some are unfamiliar with what this type of equipment is capable of. Larry was satisfied that his set was working "perfectly" several different times throughout the course of this thread. With each new development / improvement he was blown away by the performance.
I almost suggested that he replace the other .1 because Matt spoke of a bad batch. Larry came to that same conclusion but he also changed both .047s at the same time. Now it's not known for sure which one or combination of the three could have been causing the problem so I don't think that they all can be condemned based on this unscientific result. It is not known for sure that the .047's had any defect at all.

I admit that I have been too trusting. It's easy to condemn all yellow metal film capacitors as junk because of a bad batch but from my experience I haven’t run across a known bad one yet.

If you can hear a difference, then another one of the yellow jobs was bad and you hadn't found it yet.

For anyone doing serious electronic work, I recommend not referring to charts for component values. Memorize the common international standard measurement prefixes (SI) which apply across all industries and fields:

pico (10^-12)
nano (10^-9)
micro (10^-6)
milli (10^-3)
centi (10^-2)
deci (10^-1)
kilo (10^3)
Mega (10^6)
Giga (10^9)
Tera (10^12)

You can easily convert from one value to any other by merely sliding the decimal point left or right by the difference between the prefixes. No chart needed.

You should also memorize the resistor color chart. It's easy to do, and will allow you to look at a resistor and know its value by inspection. Also much easier when you have to look at a chassis and locate a, for example, 4.7k resistor.

This is from experience.

-David

Doug, I suppose I jump to conclusions too quickly. I've done this many times before, so it certainly isn't unusual. Remember, I told you my Mark I simply wasn't as loud as Golden Throat 15's 6-HF-2 that I restored a year and a half ago. The defective yellow caps turned out to be the reason.

Remember, I've had multiple problems with this set... the shorted 6AU6 tube in the tuner, three bad resistors off that tube... and the bad coupling caps in the power amplifier. It's strange that all these problems developed at one time. I am wondering if this set is haunted?

The ETR .1 yellow caps are about as third as long as the Mallory caps. Wonder if that could contribute to their shortcomings?

Larry,
I absolutely understand and I'm not trying to find fault. I have been blessed. In high school, vacuum tube theory was still taught in electronics class. My course final was on the operation of a single tube phonograph. I blew my instructor away. He said it was one of the simplest yet most comprehensive papers he had read from one of his students. I have had mentors beyond compare. Some are still close friends and a phone call away. I've had many advantages and yet I still get the occasional problem that literally kicks my buttocks around the block. Forty some odd years later I still don't really know what I'm doing. I am still learning.

I fully believe that we never quit learning, no matter how much knowledge or training or schooling we may have under our belt. This thing seriously kicked my butt for nearly two weeks, but thankfully I got a handle on it and got it fixed... with no more test equipment than a multi meter. I'm beginning to think that's all a repairman ever needs.

Doug, I didn't go to electronics school, and I've never taken a course in electronics or vacuum tube theory. Maybe I should have taken some classes, but I haven't. Everything I know is self-learned. I got started on this stuff in about 1990, restoring 1930s vintage radios. I was lucky I guess, because a simple recap of all the wax caps and electrolytics made every one of them play like a top!!!

My background is in journalism and I have a degree in it. I guess you can tell that from the lengthy threads I post on here!!! But I've always loved music...as a kid mother bought me a cheap stereo and after school I'd have both ears glued to its tiny little speakers and thought at the time that the thing sounded dammed good. I had no idea my love for music would evolve into owning the most expensive, and most professional, piece of equipment ever produced by RCA Victor.