[Ron Ramirez]

Five hours later (you read that right)...

[Image: http://www.philcoradio.com/images/phorum...00_018.jpg]

C37 is in place. All of the resistors that were connected to C37 were replaced with new ones. The 4.7K and 33K resistors look smaller than the originals but are actually 2W units (the originals were 1W).

In case you noticed - Yes, the white and yellow wires are now reversed in comparison to how they were wired previously. This is correct per Dave Gillespie (see post #32, page 3, this thread).

That was a lot of work! Time to relax. I have five more individual electrolytics and the death cap remaining to be replaced.

[Ron Ramirez]

...you know me...can never leave well enough alone...

No worries, this is a "good news" post.

After telling Debbie about my work on the TA-600, she asked if I was going to try it out tonight.

I thought about it, and decided, "Why not?"

So I hooked it up to a pair of speakers and hooked up my Terk FM antenna.

I plugged it into my Variac...and brought it up slowly...

At 100 volts it began to play - only in the left channel.

While twisting the balance control, suddenly the right channel sprang to life!

The FM is mono - no multiplex decoder as this set was built before the FM Stereo standard was finalized - but it sounds great!

So now I need to apply DeoxIT to all of the controls and switches, followed by FaderLube to the volume, bass, treble, and balance controls.

I have more work to do to it as well...five more electrolytics, the death cap, plus adding 10 ohm resistors to the 6П14П cathodes, and a mod to the phono circuitry...and this unit should then be good to go.

But I am really glad to have heard it sing for the first time in who knows when.

Note: The TA-600 does have a MPX output and stereo MPX inputs, so with an external FM multiplex decoder this receiver can pick up FM Stereo. That will come later.

[Ron Ramirez]

Good news...

So I set out today to replace the remaining individual electrolytics and the death cap.

I also used DeoxIT on all controls and switches, followed by FaderLube on all controls.

The death cap was easy. I replaced the original .01 uF "Black Beauty" line to ground cap with a modern safety cap.

Four small electrolytics...not so easy.

[Image: http://www.philcoradio.com/images/phorum...00_019.jpg]

[Image: http://www.philcoradio.com/images/phorum...00_020.jpg]

Hint: The new electrolytics are silver, made by Vishay-Sprague.

There is still one more to do. And it is going to be fun. NOT.

[Ron Ramirez]

...bad news

I turned the receiver over, connected two speakers, plugged it in through my Variac, and slowly brought it up to 115 volts.

It's Alive!

[Image: http://www.philcoradio.com/images/phorum...00_021.jpg]

Those new Hayseed Hamfest caps certainly look good on top of the chassis.

[Image: http://www.philcoradio.com/images/phorum...00_022.jpg]

But here is the bad news:

I let it play for several minutes, tuning across AM and FM bands, and it was sounding great.

All of a sudden, I started noticing a pronounced distortion in the sound!

I looked at the 6П14П tubes, and one of the poor little Russian tubes had a glowing red plate.

I immediately turned the thing off.



The distortion could be the result of audio coupling caps dying (I did not replace any of the brown caps that look like brown Orange Drops), but the glowing red 6П14П concerns me. It looks like I will be forced to install the Dave Gillespie IBAM mod in this receiver if I ever want to use it for any length of time. In a nutshell, this allows for individual bias settings for all four output tubes so they run at peak efficiency, and to avoid such red-plate situations.

It's probably a good thing I have another set of NOS-NIB 6П14П-EB tubes on their way here from Ukraine. (Maybe I should have bought two sets?)

Well, at least I made my goal of hearing this receiver play in time for my birthday (I actually beat that goal, having heard it for the first time last night). But this unit will require more work.

I need to order some CL-80 inrush current limiters for this receiver as well as my Fisher 400 and 500-B. I shall also order the necessary parts to build an IBAM board for this receiver.

[morzh]

Likely the coupling caps.

[Ed Locker]

Likely the coupling caps.

+1

[Ron Ramirez]

I've conferred with the guys at AudioKarma on this subject as well. I'll order new coupling caps this week, along with an inrush current limiter and enough parts to build an IBAM board for this unit.

I suppose I could use the yellow film caps I have on hand, but I'm going to order Illinois Capacitor film caps instead.

[morzh]

I don't see how regular yellow film capacitors are going to do worse than any other film capacitors (which in case of the IC are also yellow ) at audio frequencies.

[Ron Ramirez]

Point well taken. I've already ordered the 0.1 uF Illinois caps, but I'll just use my regular stock of yellow film henceforth.

[Ron Ramirez]

An Experiment

So I switched V21 and V22 following a suggestion by one of the AudioKarma guys. Last night the 6П14П tube which developed a red plate was in the V22 position.

I reconnected a pair of speakers, plugged the TA-600 into my Variac and brought it up to 115 volts again.

Result:

The red plate followed the same 6П14П to the V21 position. However, tonight I was able to play it twice as long as last night, and when I saw red on the V21 plate, it was red in a small spot instead of the entire plate being a glowing red as it was last night.

I had the lights out at my workbench, watching for any red plates, and as soon as I saw it I turned off the Variac.

[gregb]

Is it possible the tube is gassy, are these the new ones or the used ones? Did you measure what the bias voltage on the grid of each output tube is? As for the coupling caps I agree with the others and would just change them to be safe. Just Radio has those JBX caps which are cheap, seem to sound just fine and best of all are black. They don't have the cheap yellow cap look when installed.

Gregb

[Ron Ramirez]

Greg

These are the used ones - the NOS-NIB 6П14П-EB tubes have yet to arrive from Ukraine.

I have not yet made any measurements.

I will change the coupling caps - with yellow film caps. I understand about the stigma of yellow under the hood, but it does not bother me if they are yellow. I do not plan to display the TA-600 upside down with the bottom cover off.

[rocketeer]

Or you could jack it up on blocks and set a mirror under it.

[gregb]

I recommended those black ones because I do a lot of repairs for other folks and the blacks ones seem to get rave reviews even though I don't think there is much if any difference between them and the yellows. A lot of people seem to associate the yellows with poor quality but in my many years of using them I have only ever had one go bad and I have installed thousands of them.

Gregb

[Ron Ramirez]

Same here, Greg...I used to do radio repair for people, and like you I've probably installed thousands of those yellow caps and can only recall one or two failures. And it has been several years since those failures occurred. Not a bad record, I think.

Larry - LOL