Help Saving 400-CX SA-100 and 100-R Tuner

[dcgillespie]

The heater dropping resistor is in fact the one you have identified: 12Ω, 7W rating.

I would suggest that once you get the power supplies recapped and the bridge rectifier changed out, then you should be able to go ahead and power it up using the aftermarket transformer setup (assuming all connections are sound and correct), and then we can see what adjustments might be needed from there.

Dave

 

[moondogtn]

Finally...school's out! I am hopeful I can work over this some during Christmas break. I ended up ordering custom can caps from Hayseedhamfest. I removed one of the caps and installed the new phenolic wafer this evening. I was able to borrow a rivet gun to make the install nice and neat. I will post pics soon. I am hoping for some advice regarding the removal and installation of the caps. Its a beast to undo the old wiring. Should i just snip as close to old component as possible? This is first ever tube gear I have worked on....it's a little different that board mounted components. Looking forward to this project immensely. Thanks for any and all tips and guidance.

Bill

 

[moondogtn]

I finally got the new can caps installed. They look nice but chassis showing it’s age. Is there any safe way to clean it up and make it look better? I have heard many suggestions but I did not want to ruin lettering.

Also, quick question on the bridge rectifier, will this part be more suited for the task....https://www.mouser.com/productdetail/583-br34

I would like to place order ASAP but wanted to see if I should include anything else at this time?

Thank you.

Bill

 

[audmod01]

I am wondering if it might be possible to add a copper strap to the Triad transformer to help control hum when you get to that point. You might find the width needed at: https://www.mcmaster.com/#copper/=1b0tgg8 which would require careful evaluation of just how thick a strap you could use according to the end bells of the transformer. If you can find a correct Fisher transformer, that would be the best solution.

Joe

 

[notdigital]

That rectifier is a 3A/400V rectifier and is perfectly fine.

Can you do me a favor: Can you post a pic of the serial # of your unit? I'm working on a CX2 as well and I'm missing the S-number. It looks like it was inked on in yours which would explain why I can't see the # on mine. Thanks!

 

[moondogtn]

Audiodon, I have looked for an original replacement transformer but so far have not had any luck.

Notdogital, I thought I posted it in the google photos album but here are a few pics of serial number. I remember reading your thread just the other day. Very cool!

Order placed earlier today so should be here soon.

Bill

 

[notdigital]

Thanks Moon! That number looks like it was ink stamped. In all likelihood, that is why the number on my unit didn't last. Oh well.

 

[moondogtn]

Progress is slow but installed the bridge rectifier last night. Removed the original terminal strip and mounted to the side How does this look? I still need to clean up the flux.
I plan on leaving transformers off the chassis for testing. I hope to test tonight if I get in on time but I do need to confirm wiring.
This is the circuit that had the 120 plug going directly to the diodes. It looks like the black wire got warm/hot at some point? Maybe when someone plugged that cord in? I attached a pic but can get a better pic if needed.

I am still trying to find a single transformer that will suffice.

Thanks
Bill

 

[dcgillespie]

That wire surely did get extremely hot! What does it connect between?

Dave

 

[Sam Cogley]

I've looked for a 400C transformer for a while. Having Heyboer build one is probably the only way to go.

 

[moondogtn]

Dave, I need to trace that wire out and will post up findings.

Sam, or anyone else, regarding the transformer, do you happen to know specs for the orginal on this unit? There wasn't one included so.....for the meantime, I am going to just mount them externally on a plate or board so I don't have to modify chassis. I will still be able to perform work on the unit which wont be fast as I am doing it in spare time. Also, any idea on cost from Heyboer? I am going to start a thread here directly related to power transformer and see if I get any feedback.
Thanks

Bill

 

[larryderouin]

Bill. If you have or get a Sam's Photofact for the unit, it should have detailed info on it forthe different sections (voltage and amps). Heyboer should b able to wind a new tranny from this along with the physical dimensions of the base holes. Probably in the neighborhood of $150.00 - $200.00

 

[moondogtn]

All, it’s been awhile. I was waiting on something....I received the transformer. Here are final specs and a picture.

Here is the information for the Heyboer transformer:

black-0, black-120 Primary
red-310, red/yel-0, red-310v @ .060 mA HV secondary
white-0, brown-26v @ 600mA fil 1
green-0 blue-5.8v -yel-6.5v @ 600mA fil 2

Physically, it looks great. I twisted wires to reflect what looked original.
I am thinking I can use wire nuts for initial power up.
Suggestions appreciated for power up. I have a variac but it doesn’t have a meter...
What am I going to check?
Larry, I may need to obtain a sams photofact for reference.
BTW, price of transformer was less than anticipated. I thought it was very fair.

Bill

 

[moondogtn]

I got it all hooked up and ready to go(I think) but unsure which way to proceed. DBT or variac? I have all tubes removed.

Also, Dave, I told you I would check that wire that appears to have gotten hot. It is a ground and runs all across unit from mounting tab on C46 to Pin 5 of V2 to Pin 4 of V7 to mounting tab of C50
Anything else I should check or look for prior to applying power? How do I want switches positioned?

I won't do anything until I hear back as to the best way to proceed.

Bill

 

[dcgillespie]

You will want to do the initial test with all tubes in place except for the rectifier (6V4) tube. Before that however, I would first check the health of C46 and C50. C50 may still have some life in it, but there's a good chance that C46 could be bad. If so, it should be replaced -- and really should be replaced anyway even if the original one is still good (which I doubt). Once that's done, then power up without the rectifier tube with either a DBT or variac, whichever you prefer. The control settings doesn't really matter much with the start up, although I would set the stereo/mono mode switch to Stereo, and the Stereo Dimension control to full Stereo (control turned off). Set this way, only the two outside indicator lamps should light.

Once the DC heater voltages are verified, then you can shut the unit down, install the rectifier tube, and restart using the DBT or variac, whichever you prefer.

Dave

 

[moondogtn]

Dave, I replaced all the can caps with those from Hayseed Hamfest.
(C45, C46, and C50)
I will test the other tubes and install all except the rectifier for now.
I will have to research a bit to determine what is meant by heater voltages and where to check them but should be able to do all of this tonight. Most likely, I will use DBT for initial power up.
I will post up results. Thank you.

Bill

 

[larryderouin]

Heater references the filaments. Terms are synonomous. Small signal tubes will be 6.3V or 12.6 FISHER starved them for longevity. around 11.6 or 5.8 is in the range they starved to. I've seen some units where the 12.6 types ((usually 12ax7) are starved down to 10.6v) They are shown on the schematics as a "V" with a pin # on either end of the V. Heater strings are run off the transformer on one of the low voltage taps. These can either be AC or DC.

 

[moondogtn]

Larry, thanks! These schematics will make sense one day. I was wondering what that the V meant just the other day as I was trying to follow part of the circuit.

I used DBT and powered up. Glowed dimly for a second but then went out like it should. Removed it from circuit and set variac to 120. Using it I checked the heater voltages, basically pins 4 and 5 for all tubes except V4 which uses pins 9 and 4/5 and it is AC. I powered variac on and off in between readings as I didn’t know if I should leave it on the entire time.

Following are voltages

V1 11.6
V2 11.2
V3 10.9
V4 6.9VAC
V5 11.05
V6 11.05
V7 10.9
V8 11.6
V9 11.6

Bill

 

[larryderouin]

Looks good. Fire it up and hook it up to an amp and a source and let her fly. One Down Two to Go. Be careful, you're doing good.

 

[moondogtn]

Hahaha. I appreciate the encouragement but it will have to wait until tomorrow. It’s midnight and work will come early. I’ll keep you posted. I think I know I still have plenty of work to do on this one but I am glad it’s functional.