DS100 selection problem

Hey all,

Trying to track down a problem. I have a DS100 that I fixed up a few years back its been humming like a bird for the past 4 years. All of a sudden it stopped selecting, doing the dreaded two pass and stop.

The one curious thing is that if I pop out and reseat the 2050 tube, the selections will work properly for about two songs then stop working again. I have tried two 2050's (both old) and the same thing happens. If I shut it off and let it rest it still doesn't work till I reseat the 2050. I ordered a new 2050 and a new 12AX7. The 12AX7 showed up today, no effect. The 2050 should be here later in the week.

Went through the service manual troubleshooting with no luck. Everything seems to be working okay. The battery test works, it will select every record. The pulse amp seems to work. I don't have a seeburg lamp tester but using a meter seems to be checking out.

Any ideas?
Thanks!

Are you sure about what you have written here ? If it works "every time with the battery", "popping the 2050", should not enter the picture--that is the read-out section, which has been proven good with the battery test ?? ? Ron Rich

Pedro, it is probably the 2050 -they are a pain in the ass as they age (just like people).

Try this: get the machine to play, look at the top of the 2050 tube in the area where you see the orange cathode glow. Hit the reject button. you should see a violet glow for a second. If the glow is light blue the tube is definitely weak.

One of the "joys" in using thyratrons is that as they age the ignition point becomes slightly delayed as the cathode has less emission and has to be forced to conduct by the extra heat generated when the plate is trying to draw electrons from it. What this means is that the short pulse to trip-select is sometimes too short in this condition. The end-trip has no such limitation as the trip switch stays closed till the tube gets it's self together. (if it ever does).

I assume the pulse amp has a replaced 0.47cap and the 5.6 megohm resistor has been checked. Has the cap between the pulse amp and 2050 been replaced?

Rob/NYC

Rob,
I greatly represent that statement--I am "old", but not yet a PIA--I hope !
BTW--I agree, but did not think he could have two "bad" 2050's )
Ron Rich

Ron Rich wrote:Are you sure about what you have written here ? If it works "every time with the battery", "popping the 2050", should not enter the picture--that is the read-out section, which has been proven good with the battery test ?? ? Ron Rich

This is why I am confused, the battery test causes all of the selections to be played which makes me think its a Write In problem, but selections work perfectly fine when I pop the 2050 and plug it back in this is something I have tested 4 or 5 times swapping the two 2050's I have (the one from the stepper and the one from below the Pulse Amp) Each time it works fine and selects properly for the first few minutes then reverts to the two scan and done.

I haven't done any work on the Pulse Amp myself since I have owned the unit so I will check into Rob-NYC's tips when I get home.

I am of the opinion, it's not the PA. As I see it, if it were the 2050, or the PA, it would show up when you did the battery thing--? How did you do the battery test--did you check for sure, that each and every selection played ? Did you use the "reject switch" on each selection, or did you hold down on the detent lever ? By any chance, does the TSU still have a germanium diode in the wright-in voltage limit, circuit ? Did you check all voltages ??
Have you cleaned the insulated portion of the K contacts in the USPU-1 ?? Ron Rich

I waz thinkin' on this problem sa-more--
How long has it been since the tubes/ caps were changed in the TSU--also--didja check the 2 watt 56K resistor--and the 36 ohm-1/2 watt, that is right next to it ? These both have a "liking" to change value----Ron Rich

Its been about 4 years since the tubes were replaced, I swapped them all out when I bought it. The caps haven't been touched since I owned it. The previous owner said he did most of the electrical work about a year or so before I bought it. I can't say what he did. He did install a free play adapter. I have the credit unit but its not in working order and I removed it from the machine. (the plastic gear is chewed up) I also disconnected the stepper to try and get rid of any extraneous problems.

The battery test, I started the carriage, grounded the negative to the skin of the PA and touched the RCA to the positive. It started picking up each record in order. I rejected the first ten or so records with the reject switch, I did not go through the entire carriage.

I will put more work into it tonight, thank you for giving me some new things to look at I will report back soon.

Pedro, here are the write-in and read-out circuits for the tube era Tormat machines:

http://s1192.photobucket.com/user/Rob-N ... e.jpg.html

http://s1192.photobucket.com/user/Rob-N ... 3.jpg.html Hover mouse over pic and click the fourth gray button to enlarge the pic.

The circuits are extremely simple and most problems outside of tubes are capacitors, resistors and poor contacts.

If the previous own did only halfway measures, it will be time to finish the job.

If possible take clear pic's of the parts side of the two chassis pans and post them so we can get an idea of what, if anything, was replaced.

Rob/NYC

Haven't had a chance to dig back into it yet, stupid life getting in the way... here are some photos I snapped tonight

https://www.flickr.com/photos/43838031@N04/

Looking at the caps, it looks like the previous owner did a rebuild of the Amp, lots of new parts on that side but the TSU has gotten very little love.

I ordered a whole new set of tubes for the TSU should be coming in in the next few days. I was hoping to have this guy up and running by the weekend because I have a ton of people coming over but its looking like i'll miss my deadline

No way that is a complete recap. he did replace the main electrolytics but not the critical smaller caps.

The write-in time constant cap is right above and slightly to the left of the gray selenium rectifier -behind a few resistors.. That one is important. It is rated at 0.068 which you can make up with an o.047 parallel with an 0.02. I've used a 0.1 there in a few instances.

Also, the circuit uses positive-ground so the cans of the electrolytic caps are at high potential. they should have a few layers of electrical tape around them and the clips should not be too tight. if those cans make contact with the chassis it will kill the 6X4 and probably the transformer.

I suggest adding a 1/5 amp slow-blow fuse in series with Pin-7 of that tube. use an inline holder. that will help protect the transformer.

Rob/NYC

Also, I notice a link is open on the screw panel. If those are the E and D links, opening them will disconnect the write-in pulse.

Rob is correct--the links appear to be open--however, check as to which ones are supposed to be closed (see schematic), as it also appears that the "open link" is in-correctly attached ? I think he made a "typo", and meant to call out that fuse as a 1/2 amp SB ?
IMHO, a total replacement of all "lytics", and "paper" caps is needed, and a total resistor check--plus that germanium diode, MUST be replaced (1N4002, or better). Ron Rich

Ron, Pedro, the E and D link are the W-I coupling and they don't appear to be properly connected.

Ron, you are right about the typo, I meant to write a ½ amp/slo fuse. A ¼ amp/slo might be better though.

I could suggest leaving the link open and doing a continuity check to chassis ground while simultaneity pressing each letter end number (A1 through V0) and looking for low resistance, however, with the critical caps not replaced -that- needs to be done first.

Rob

I opened up that link doing one of the troubleshooting tests from the service manual it wasn't that way when I was having the problems. I ordered a TSU Cap kit from Victory Glass, I'm assuming that is a complete kit. I have a 6x4 and a pair of OA2's coming in today, I should have a 2050 in tomorrow. I really hope that should cover me. (If all else fails replace everything right?)

Thanks a ton for the advice, I will drop a fuse in line when I start the recap process.

I am working on the recap and I have four caps that are just labelled "pulse amp"

1-474k 400
2-2a682gt
1-473k 630

Anyone know where these go (yes, I know the pulse amp) I dont know cap ratings well enough to decipher from the schematics.

Forgive me for my novice newbieism!

Thanks
-Jason