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Post by robnyc on Jan 5, 2017 9:55:59 GMT
Norman, we have to find out that cause of low bias on the trip tube.
So, try these tests -exactly- as described;
Remove --all-- plugs external to the TSU, no mech, credit unit kbd.
Remove the pulse amp. It should never have an effect on bias, but take it out anyway.
Remove the 2050 tube.
Plug in the TSu and read the LVDC starting at the rect, then through the 470K and filter then on both sides of the 1 megohm resistor and both sides of the 470K at Pin5 of the tube socket. You can expect to see a slight drop after the 1meg resistor due to the fact that most DVM's are a 10 meg load on the circuit. The reading at Pin 5 should be somewhere in the 20's (volts DC).
If correct, put the tube in and see if the reading changes. If you see a dramatic change it means that the tube has become gassy and must be replaced. Actually, thyratron tubes do have gas as designed (usually mercury) but this can become contaminated by gassing-off from the glass and metal parts due to heating.
Rob-NYC
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Post by Ron Rich on Jan 5, 2017 15:53:35 GMT
Hi Norman,
OK--It was an AY160 U model at the time it left the factory--does it have a RCSU or a TJU, and which number, installed in it ? Ron Rich
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Post by vaguy22 on Jan 5, 2017 19:52:29 GMT
Hi Rob and Ron. Ron Juke has RCSU2 which is disconnected for voltage test. Rob:with ALL plugs disonnected including those to the RCSU2 And the pulse Amp and the 2050 tube voltahe is7 volts it creeps slowly from 2 to 7 in 10 minutes. to review all caps replaces all resistors are within 5% of marked value. voltahe at rectifier is negitive 28 volts. rectiver is original to the TSU. Again thanks to the both of you for youer help. Norman
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Post by Ron Rich on Jan 5, 2017 20:29:56 GMT
Norman,
If it's 28 on one side of the 470k ( which it should be) and 2-7 VDC on the pin 5 side, with no tube in the socket--it's GOTTABE a shorted tube socket--or wire there-on ! Remove the wire on pin 5--measure it -- lift resistor, if not 28, --could be the resistor is shorted to ground (solder splash ?)--- Ron Rich
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Post by vaguy22 on Jan 6, 2017 0:28:34 GMT
Hi Rob and Ron. Removed wire from pin 5 of 2050 socket. checked voltage on 470 K resistor still 6 volts. this is with chassis on workbench.Installed new bridge rectifier 200 volt @ 6 amp. here are the voltages down the line. at - side of rect. 28 v. after R533 (1800 ohm) 18 volts. after R 521 ( 470K) 15 V. after R508 (1 Meg) 7 V. after R510(470K) 6V. Reference page 13036 of seeburg manual for TSU7. Thanks Norman
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Post by robnyc on Jan 6, 2017 2:07:43 GMT
Norman, can you give us make 'n model of the meter you are using. It sounds like it may be loading the circuit.
Rob
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Post by vaguy22 on Jan 6, 2017 2:37:28 GMT
Hi Rob. Meter in use is a Craftsman digital model--822141 I also have a RCA voltOhymist VTVM. would that be better? Thanks Norman
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Post by vaguy22 on Jan 6, 2017 2:44:58 GMT
Rob Just tried the VTVM it shows 10 volts on pin 5 of the 2050. Thanks Norman
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Post by Ron Rich on Jan 6, 2017 3:42:35 GMT
Norman,
By any chance is that an AC reading, or "plus" DC reading ? Is the wire removed from pin 5 in this reading ? Ron Rich
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Post by vaguy22 on Jan 6, 2017 4:00:08 GMT
The wire has been reconnected to socket. checked socket for short to ground checked ok with wire off pin 5. the 10 volt reading on the VTVM was on the -DC 50 volt scale.reading was taken with the wire replaced on pin 5 of the 2050 socket. thanks, Norman
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Post by robnyc on Jan 6, 2017 14:05:10 GMT
Norman, your DVM should be fine. They all have 10meg DC loading.
I pulled out a TSR-3 and after allowing the caps to form for a few minutes (unit last powered in Mar 07) We read:
30.3 @ rect.
29.2 @ filter 25mfd Here i seem to have used 50mfd -probably because I had them. It would make no difference.
25.3 @ Pin 5. This is typical.
Line voltage 121.2
I can't find a 2050 since I haven't used those in over 20 years, but if you are not getting similar minus at the socket even without the tube, that must be dealt with first.
BTW: I assume you are measuring to chassis ground.
Rob
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Post by vaguy22 on Jan 6, 2017 14:30:48 GMT
Good morning guys. Rob. yes I am measuring to ground.I am supicious of the 1800 ohm resistor connected to the rectifier I have a 222 manual showing a schematic of a TSR3 and there is NO 1800 ohm resistor in the TSR3. I am loosing 10 volts or so through that resistor. Thanks again both of you for your help.Norman
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Post by robnyc on Jan 6, 2017 15:23:20 GMT
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Post by Ron Rich on Jan 6, 2017 15:25:17 GMT
Norman,
If you have a U model phono--they added a third resistor in the -DC area--off hand, don't recall value but 1800 sounds correct ? Above, you ref'ed the TSU-7 schematic--that should show the 3rd resistor ? Ron Rich
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Post by robnyc on Jan 6, 2017 15:40:21 GMT
Ron, I have a TSU-7 code B in front of me w/date code of mid-'62. There is no 1800 here. other than my splitting the filtering of the trip and stepper the ckt is identical to the schematic i linked. You may be thinking of a different phono...no surprise give how long this topic has become.
Rob
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