UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Telephony and Telecomms

Notices

Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

Closed Thread
 
Thread Tools
Old 2nd Apr 2018, 9:52 am   #1
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Creed 75 teleprinter

Hello All, I've recently come back to my interest in teleprinters and I'm trying to get my Creed 75 working. I have a 7B which is a going concern but the 75 has been left unloved for some time and needs to be sorted! I'm way out of my comfort zone of broadcast TV gear with this - that's part of the attraction - and I want to go on air with RTTY once things are sorted.

After a lot of battles with the Heavy Metal software because using a USB to RS232 is a can of worms, I've gone back to an old Windows 2000 laptop with a real RS232 output. That's giving clean signals to drive the BARTG interface unit which I've modified to run single ended drive (which my 75 is configured for).

No matter what I do, all that I can get out of the 75 is the letter 'T' with a few 'L's and 'H's. It works fine from its keyboard but this machine does not have an internal 'loop back' and runs the translator directly, so that may not be telling me much.

I've adjusted the magnet operation as per the book and all seems well, but still just a mass of 'T's when I'm pretty certain the Baud rate is correct and the input signal looks good on a 'scope.

Any experts out there on the 75? What am I doing wrong? My machine is very clean, well-lubricated and in excellent condition, so what's likely to be the problem? Random garbage is to be expected with a faulty or wrong format teleprinter, but all these 'T's?

Any clues gratefully received.

Many thanks.

Paul M G8MJW
PaulM is offline  
Old 2nd Apr 2018, 10:27 am   #2
lesmw0sec
Octode
 
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
Default Re: Creed 75 teleprinter

Does your software include the necessary start/stop bits?
lesmw0sec is offline  
Old 2nd Apr 2018, 10:29 am   #3
wireless_john
Heptode
 
wireless_john's Avatar
 
Join Date: Apr 2011
Location: Gosport, Hampshire, UK.
Posts: 597
Default Re: Creed 75 teleprinter

Have you got two stop bits, one might not be enough?
__________________
GQRP Club 4704 - BVWS Member
wireless_john is offline  
Old 2nd Apr 2018, 10:34 am   #4
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: Creed 75 teleprinter

Yes, the start/stop information comes from the standard 'Heavy Metal' interface software which has multiple menu options for word length, coding format, stop bits (1.5 in this case should be right) and baud rate. The original program is here: http://www.buzbee.net/heavymetal/Intro.htm
I've used this many times with my 7B but there's a newer version which should work with 64 bit computers - I can't make it work - so I've gone back to this original version running on an old Windows 2000 laptop. I know that's worked in the past and the 'Heavy Metal' program is well known. It all looks good on the 'scope so I suspect it's a problem with the 75 itself.

Best regards,

Paul M
PaulM is offline  
Old 2nd Apr 2018, 12:14 pm   #5
wireless_john
Heptode
 
wireless_john's Avatar
 
Join Date: Apr 2011
Location: Gosport, Hampshire, UK.
Posts: 597
Default Re: Creed 75 teleprinter

Are you able to tell if the correct character is transmitted when a key is pressed even if the wrong one is printed? That might narrow it down to the aggregate motion levers?
__________________
GQRP Club 4704 - BVWS Member
wireless_john is offline  
Old 2nd Apr 2018, 12:32 pm   #6
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: Creed 75 teleprinter

I assume that you mean in local mode? The 75 doesn't have a true local loop in local mode - that is, apparently, the reason the GPO didn't like them as it's not a 'true' local record. In local mode the keyboard works the translator directly and that's all working absolutely fine.

What I haven't tried yet is wiring in the transmit side of the loop to see what the true Baud rate is on the machine and whether that side is working. Making it work in receive is the prime goal at the moment and I believe that the fault is something to do with the mechanical input side of the machine. The armature is moving properly and it's been adjusted as per the book for single ended drive. It's all very positive sounding and looking on that front with the clutch working properly on receipt of a signal.

I really do need to check the Baud rate on transmit but it's a dual speed 45.5/50 machine with a gearbox and 'Heavy Metal' can work over all the known standards (which I've tried, just on the off-chance).

Are the aggregate motion levers in play only on receive? I'm not familiar enough with the system to know.

Many thanks,

Paul M
PaulM is offline  
Old 2nd Apr 2018, 2:17 pm   #7
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Creed 75 teleprinter

Talking out of my head, but have you got the polarity correct? caused me all sorts of problems when setting up my I-Telex system
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 2nd Apr 2018, 3:32 pm   #8
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: Creed 75 teleprinter

The polarity is switchable on the BARTG interface and it makes no difference other than the wrong way makes the clutch engage all the time.

Cheers,

Paul M
PaulM is offline  
Old 2nd Apr 2018, 6:53 pm   #9
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: Creed 75 teleprinter

I don't know this machine at all, but the manual is on Sam Hallas's site, and I've been looking at it...

I think you need to find out where the signal is getting lost/corrupted. Send one character at a time. Look at the output of the computer with a storage 'scope or logic analyser, does the signal there look right (correct pulses, correct timing?) Then look at the signal going into the teleprinter magnet. Does that look reasonable?

According to the manual, the 'selector' unit in the Creed 75 should take the incoming serial mechanical signal from the magnet and convert it to parallel on 5 pins that slide to and fro. Do those pins get set to the right states? Are they then transferred to the agregrate motion linkages?
TonyDuell is offline  
Old 2nd Apr 2018, 7:23 pm   #10
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: Creed 75 teleprinter

Hello Tony,

Yes, I've already looked at the codes out and they are correct. RYRYRY being the easiest to see and work out. The timing is also correct (it wasn't when using USB to RS232). The electrical part is easy compared to the mechanics - I know what I'm doing with that!

I have previously downloaded the whole manual from Sams's site and it's very complicated.

I am fairly certain that the fault now lies in the mechanics of the Selector Unit as 'someone' has been there before and there was a loose end float adjustment screw on the rocker shaft. That's now been set as per the manual but it still doesn't work properly other than I do now see a few other characters occasionally.

The Selector Unit controls start/stop and also via a series of cams further down the chain, the Aggregate Motion selectors. The start/stop clutch appears to be working and is adjusted correctly.

This machine is very complex.

Many thanks,

Paul M
PaulM is offline  
Old 2nd Apr 2018, 7:31 pm   #11
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: Creed 75 teleprinter

At least with the mechanical side you can see what is going on, what is moving, etc.

I debugged my Creed 7E (after totally stripping it, cleaning it and putting it back together -- without a manual) by turning the motor round by hand and moving the magnet armature to simulate incoming bits at the right time. Watched as it sampled the state of the appropriate lever and set the parallel levers correctly.

Note that a machine that will run by hand like that may not work at full speed if parts are sticking. But a machine that will not work by hand will certainly not work at full speed.
TonyDuell is offline  
Old 17th Apr 2018, 7:02 pm   #12
woodchips
Octode
 
Join Date: May 2010
Location: Grantham, Lincolnshire, UK.
Posts: 1,172
Default Re: Creed 75 teleprinter

Many of the 75's were 50/75 baud?

With the machine running, but not doing anything, quickly toggle the receive magnet over and back, this will print a character. If it prints pretty well the same character each time then you can work out what the mark and space bits are, are they sensible?

Tony's suggestion of hand rotating the motor is a good one, trying to get my 7RP to decide not to keep sending the answer back, like you say, complicated.
woodchips is offline  
Old 17th Apr 2018, 10:10 pm   #13
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: Creed 75 teleprinter

The baud rate is correct - I've verified it by timing the output stream on a 'scope. Turning by hand hasn't thrown up any clues and I think that Tony may be on the right lines in that it's possibly not working properly at signalling speed.

I've had to put this on one side for a while, but I have now centred on the 'special screw' adjustment on the rock shaft as having being over-tightened (not by me). It's actually sheared off and only staying in place by virtue of the spring and plate surrounding it. It looks to me like the rock shaft is too stiff. It moves, but possibly not fast enough. Sadly, to drill out the sheared-off screw will need a lot of disassembly and it will have to wait. I'm not entirely sure why this might result in nothing but 'T' (and the odd 'H' and 'L') but 'T' is mark and four spaces and that could be all that it can manage due to not being able to respond to subsequent 'rocks'. 'Somebody' has been there before me given that the 'special screw' is sheared and there's signs of 'chewing' on another screw head in that vicinity. Elsewhere the machine is in mint condition, but not around the rock shaft.

I've discovered that these are very complex machines and not easy to work on.

Thanks for further advice, but I won't be back to this for a few weeks now.

Best regards,

Paul M
PaulM is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:37 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.