Notifications
Clear all

1977 Ferguson 3734 ColourStar: Thorn 9600 Chassis

Page 16 / 20
 
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

OK Chris

Well if it helps I can lend you my syclops board to try in your set?

ReplyQuote
Posted : 12/06/2018 11:05 am
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

Thanks Mike but I will decline your kind offer.  ? 

The reason being its way too risky with the postal system, I just don't trust them one iota, you can guarantee because we don't want anything untoward to happen, it will.

9k6 sets are rare enough, SYCLOPS MK11 spares are even rarer than hens teeth. 

I'm in no hurry to fix it, the only thing dented is my pride as I hate being defeated. 

ReplyQuote
Topic starter Posted : 12/06/2018 11:11 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

No problem. I'm good until Thursday if you want any readings from my set

ReplyQuote
Posted : 12/06/2018 11:15 am
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

I thought R522 was a 10%, checking data R522 is a 2% tolerance. Therefore +/- 0.014R it would be right to state R522 is out of tolerance but would it cause the troubles? I've no idea, likely not, what does yours measure?

ReplyQuote
Topic starter Posted : 12/06/2018 11:21 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

I'll check later after work for you

ReplyQuote
Posted : 12/06/2018 11:28 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

I'm sure there is a similar resistor in the 9000 0.47R rings a bell

ReplyQuote
Posted : 12/06/2018 11:29 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

Looking at the measurement comparisons I noticed that TSB/4 is 0.394V on your set, whereas mine came in at 0.250V. This could be because your R522 is out of tolerance.

ReplyQuote
Posted : 12/06/2018 1:30 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

Agreed and although mine is 144mA higher than yours its still (just) within the range expected, 400mA, according to (if its now to be believed) the manual. That in mind I'm inclined to think its likely not the cause but what do I really know?

I would suspect others such as R518, R519, R530 and R523, the former part of shaping the driver output and the latter part of controlling the overshoot and rate rise of the collector. However, all are within tolerance.

ReplyQuote
Topic starter Posted : 12/06/2018 1:46 pm
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

Mine comes in at 0.74 ohm

r522
ReplyQuote
Posted : 12/06/2018 4:11 pm
jjl
 jjl
(@jjl)
Trusted V-Ratter Registered
Posts: 85

Chris and Mikey

Don't forget that your meter's test leads are likely to register a resistance of 0.2 ohms or so; this additional series resistance needs to be taken into account when measuring such low resistances. If your meter has a "relative" function it should be able to do this for you.

Apologies if you've already thought of this.

 

John

 

ReplyQuote
Posted : 13/06/2018 9:25 am
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

Hi John,

When I reported my R522 it was an in circuit reading, naughty as I should have removed it.

With my new DMM whenever I do resistance readings I always delta (zero) my leads, the Metrix has "relative" and here it shows removed from circuit R522 (middle reading) is on the money at .75R

MyR522
ReplyQuote
Topic starter Posted : 13/06/2018 9:48 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

Point taken John, but I used some short test leads and had set the meter to low ohms, high resolution. Then I used the delta function to zero out any lead resistance before measuring the resistance ? 

 

ReplyQuote
Posted : 13/06/2018 11:14 am
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

As an experiment I decided to reduce the peak flyback voltage on my 9k6 as close to Chris's as I could and see what voltages I got on TSA & TSB

TSA B  WITH PFB 540V

My EHT facsimile voltage is a lot lower

 

 

ReplyQuote
Posted : 13/06/2018 4:10 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

Hi Mike,

Thanks for that, a very good idea  ? 

 TSA/4 TSB/4,5,6 are interesting however I've still absolutely no idea what it all means or what to do next.    ?  

ReplyQuote
Topic starter Posted : 13/06/2018 4:43 pm
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

I'm clutching at straws I guess but with the peak flyback still at 540V and the tripler input disconnected the EHT facsimile voltage dropped to 16.31V

Might be worth disconnecting the tripler and see what voltage you get at TSB/4 if it is 10-14V lower than your earlier reading youcould try turning the peak flyback up towards 650v and see if the set still trips?

If you haven't already it might be worth checking through the components in that part of the set?

1868 trip 2
ReplyQuote
Posted : 13/06/2018 5:03 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839
Posted by: Mikey66

I'm clutching at straws I guess but with the peak flyback still at 540V and the tripler input disconnected the EHT facsimile voltage dropped to 16.31V. Might be worth disconnecting the tripler and see what voltage you get at TSB/4 if it is 10-14V lower than your earlier reading youcould try turning the peak flyback up towards 650v and see if the set still trips?

I think you might be onto something here.

When I disconnect the input to the tripler TSA/4 (EHT facsimile) unlike yours it does not drop but remains unchanged, it still sits at 33.4V. However what does rise is TSA/9 (Peak fly-back), that goes from 537V tripler input connected, rising to 609V with the tripler input disconnected. I cannot adjust R613 to obtain higher as its at max extent.

Out of interest whilst monitoring TSA/9 I tried adjusting R612 (currently at mid point), this only seemed to have the effect of loading the PSU and I heard the channel lock go as the 80V (67V rail in my case) collapses.

 

 

ReplyQuote
Topic starter Posted : 13/06/2018 8:15 pm
Jayceebee
(@jayceebee)
Noble V-Ratter Registered
Posts: 1627

Ooo, now that is a clue. I mentioned earlier about the small diodes connected to the zeners on the trip rail, are you absolutely sure about them, particularly W523? Might be worth replacing it to be absolutely certain. 

Could you check the voltage at the junction of W520,521 first please?

ReplyQuote
Posted : 13/06/2018 8:29 pm
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

Glad you didn't get confused by my typo... all the mentions of TSB & TSA  confuse me ?  ?

I see VT814 is a nice nasty lockfit. Got to be worth a few minutes checking over this area. It is a pain removing the timebase board though.

 

ReplyQuote
Posted : 13/06/2018 8:37 pm
Jayceebee
(@jayceebee)
Noble V-Ratter Registered
Posts: 1627
Posted by: Mikey66

I see VT814 is a nice nasty lockfit. Got to be worth a few minutes checking over this area. It is a pain removing the timebase board though.

 

I think it would be prudent to replace both VT803 and VT814, I'm kicking myself  ?  ? 

ReplyQuote
Posted : 13/06/2018 9:01 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

W523 perfectly OK

VT803 (BC327), tests OK

VT814 was not a lockfit, at some point in the past it has been changed for a BC237, it too is perfectly OK.

ReplyQuote
Topic starter Posted : 13/06/2018 9:19 pm
Page 16 / 20