[GreenKeys] strange printing with LPR?

Fri Aug 25 22:06:17 EDT 2006

Upon Bob's suggestion, I found something interesting...First, I have a polar relay in the LESU that is keyed by my external loop. The relay, in turn, keys an internal loop. This is a polar relay and if I understand correctly, it is biased such that it will operate from an external neutral loop. 

I noticed that when the ASR was off, but my st6 was receiving ITTY, the polar relay could be heard but very faintly. With the ASR still off, I switched in my LPR and the polar relay started clicking away like a woodpecker! I also found out that it seems that even with the power off to the ASR (using the front lever switch) there is still internal loop power! Just no motor power. 

So I began to wonder...Could I have the selector magenets on either the printer or the lpr wired in parallel, but perhaps out of phase? If I have two selectors S1 and S2 and each has connections A and B they could be in parallel two different ways: 
S1A=S2A 
S1B=S2B 
OR 
S1A=S2B 
S1B=S2A 

I am not sure what this means, but could this somehow be involved? Or does it not matter?  Should I care that the polar relay is very loud when the lpr is switched in?

I will try to play with the polarity of the magnets and will also try to play with the range adjustment on the printer magnets as Gil suggested.

Eugene
thanks so far!

>-----Original Message----- 
>From: ROBERT LAAG [mailto:RLAAG at PACBELL.NET] 
>Sent: Friday, August 25, 2006 08:35 PM 
>To: 'Eugene Hertz' 
>Cc: WA5CAB at cs.com, greenkeys at mailman.qth.net 
>Subject: Re: [GreenKeys] strange printing with LPR? 
> 
>I HAD AN IDEA BASED ON YOUR RESULTS... IF YOU CONNECT THE LOOP CURRENT 
>METER AGAIN TO THE SEL MAGS ON THE PRINTER, AND THEN TURN ON THE REPERF 
>AND SEE WHAT HAPPENS TO THE READING... MAYBE THE RESISTANCE OF THE 
>RELAY IS HIGH AND CAUSES THE CURRENT TO BECOME LESS... WHEN ADDING 
>ANOTHER DEVICE INTO THE LOOP THE CURRENT COULD DROP A BIT BUT SHOULD NOT 
>DROP BY A BUNCH... THE LOOP CURRENT THRU THE REPERF SHOULD BE OK SINCE 
>IT IT DOING ITS THING OK AND PROBABLY ISN'T IMPORTANT... CAREFULLY... BOB 
> 
>Eugene Hertz wrote: 
> 
>>At several people's suggestion, I measured the internal loop current, here's what I did... There are 4 terminals on the two lpr selector magnets. My selector magnets are connected in parallel. So I have two wires coming from the internal (LESU) loop to the two connections on one lpr selector magnet, then these two connections go over to the other two on the other selector magnet in parallel. 
>> 
>>I disconnected one of the loop wires from the lpr selector magnet and inserted my ammeter between one wire from the loop and connected the other side of the ammeter to the terminal on the selector where the wire used to be. 
>> 
>>I put my ST6 on standby and read 0.05A (50ma) going through the lpr. When I disconnected the 28ASR from the jackfield, it read 0ma. So that seems pretty good. 
>> 
>>I have not figured out a way to insert my ammeter into the internal loop without the lpr also in the loop. Is it possible that with the lpr out of the loop that I would get something more like 60ma? And could that 10ma be the difference between working and not working for the printer? 
>> 
>>Is there anything mechanical that can be set on the printer to make it more sensitive to a (potentially) lower current? I should mention that there is a rheostat in the LESU for the loop current, but it was maxed out when I took the reading of 50ma with the lpr in the loop. 
>> 
>>I will add, then when I got the ASK from Mr. Hart. He did suggest I remove the internal loop and just use the external loop (from the ST6). I think this was more of a way to guard against an eventual (inevitable) failure someday of the LESU. 
>> 
>>Eugene 
>> 
>>-----Original Message----- 
>>From: WA5CAB at cs.com [mailto:WA5CAB at cs.com] 
>>Sent: Friday, August 25, 2006 06:49 PM 
>>To: ehertz at tcaf.org, greenkeys at mailman.qth.net 
>>Subject: Re: [GreenKeys] strange printing with LPR? 
>> 
>>Eugene, 
>> 
>>I don't know what kind of loop supply you are running and if you said it's the one that comes with a 28ASR I still wouldn't know, having owned M28 stuff but never used it. But the first thing I'd do would be to patch a 0-100 MA meter into the loop (everyone really should have one permanently installed but few do) and check the loop current. It should be either 60 MA or 20 MA with nothing being sent, whichever way your machine is wired. Sounds like your typing unit may be more sensitive to it than the reperf. 
>> 
>>And depending upon what type loop supply you have (upstream voltage and current setting type), you may have to always adjust the loop current anything you go from one to two sets of selector magnets. Usually, with a 120 VDC supply, the change is minimal but I've heard some on here claim 40 volts is plenty (which I don't agree with but that's another story). 
>> 
>>In a message dated 8/25/2006 6:26:05 PM Central Daylight Time, ehertz at tcaf.org writes: 
>>Ok, so my next problem. I have not been punching tape with my M28ASR in a few weeks since the tape jammed and I was too lazy to clear it out. So its been a while. Today I cleared the jam and was printing off ITTY very well. I decided I would try to punch some tape off the loop. In my ASR it has a local loop supply that is keyed with a relay from the external loop. Everything was working fine until I switched in the typing reperf (yes I have the reset bail manually cleared from the code bars). I should mention that the main knob is in the K mode for this. 
>> 
>>When I do this, the reperf perfs perfectly fine, however the printer which is now in series with it, starts to print junk. When I take the LPR out of the loop it returns to printing normally again. I have a switch at the operators position of the ASR to switch the lpr into the loop. 
>> 
>>Any ideas? Whats baffling is that the reperf perfs away correctly, not a missed character. I would think that if the loop was being bogged down somehow by adding in the lpr that both the printer and the lpr would be degraded. There is an adjustment for the internal loop (I have never tried to measure the internal loop voltage) but I wonder if I may need to tweak? 
>> 
>> 
>>Robert Downs - Houston 
>><http://www.wa5cab.com> (Web Store) 
>>MVPA 9480 
>><wa5cab at cs.com> (Primary email) 
>><wa5cab at houston.rr.com> (Backup email) 
>> 
>> 
>> 
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