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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Wed 11, 2004 7:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 420
Location: Winnipeg, Manitoba, CANADA
This is a strange problem with my newest Eico 666. All voltages seem right, and the tester gives readings that agree with three other 666's I have. However, the Line Adjust test simple will not center the meter needle. The heater voltages move along with the Line Adjust potentiometer, so that isn't the trouble. <BR>What I decided to do, just because I have no fear, was to remove R19 that was in series with the Line Adjust calibration pot. I took a decade box, and found a resistor value that would give me a good range to the calibration pot. It was 270K; it is now much lower. Many resistor values will work, but to get the biggest range to the calibration pot (i.e. center of the calibration pot rotation) I have to use 15K!<BR>I don't know what to think. I reread Mr. Douglas' section on the 666 many times; the selenium rectifier has already been changed; but it looks to me like it is for the bias supply and the leakage test! I will think about changing everything there 'again;', just to do something. Unless anyone else has an idea.<BR>I thank anyone for any hints, tips, or even insults suggesting that I have waaaaay to many 666's. <P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Wed 11, 2004 8:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
You know that voltages in the tester track with the line adjust pot. You don't know that the Eico's meter tracks with applied voltage--which it must do to read the line properly. That's all the meter is doing during the line adjust function--reading the rectified voltage delivered by the diode in series with the resistor you mentioned and the cal pot. Nothing really to look for elsewhere.<P>Hook a digital volt meter to the 666 meter while in the tester. While changing the line adjust--Observe the reading of the Eico meter relative to the digital one. The Eico meter could have a sticky spot. It may stick, and then jump beyond the center line. That seems like it has to be the problem to me--unless I am not understanding the symptom. There are two rectifiers in the Eico--did you change both to diodes?<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Wed 11, 2004 10:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10748
Location: Mpls, Minnesota
Randy<P>The line adjust circuit is used in series with the leakage test circuit, check your leakage cal circuit first. Make sure your line adjust control is set to provide 130 vac on the high side of the primary of the power transformer. You should have 50 vac to CR-1 and approx. 50 vdc after CR-1. Check all the components in the leakage calibrate circuit including the diode and capacitor. Calibrate the leakage pot before doing the line pot.<P>You will notice the leakage and line circuits use the identical components and the resistance in each circuit should be the same. This is explained in the manual.<P>Don’t worry about the other diode as it is used for transistor testing.<P>Dave<BR><P>------------------<BR>Intelligence is the ability to use your knowledge


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Wed 11, 2004 11:45 pm 
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Location: Winnipeg, Manitoba, CANADA
I kinda sorta did it that way. I remember having 50VAC going in to the rectifier and about -70VDC coming out. My guess is the silicon diode I used is just not dropping as much as the old selenium girl. The leakage calibration works like a charm. I didn't track the Eico meter with a VOM just to compare; I just noted that the line adjust could take the filament voltage from say 5VAC to 7VAC, when set on 6.3VAC. That made me suspect that the wire-wound pot is OK, and that it is functioning as it should. But, now I have three 666's opened up, and I am doing a lot of side-by-side comparisons. Somethin' ain't right, and I'll get to the bottom of this. Eventually. Dave and Chris have given me a lot to go on. Thanks.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Thu 12, 2004 12:41 am 
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I had a 666 with a line adj pot with leakage, must of had some of those wiskers inside. Replacing the pot solved the problems. Check both of the pots, line and leakage, by disconnecting the wires and then do the ohms testing to ground from all terminals.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Thu 12, 2004 11:28 am 
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Location: 07450, New Jersey
I had a 666 that the meter adjust did not have enough range. I found the meter cal pot had developed an internal resistance path to chassis ground. Replacing the pot solved the problem.<P>------------------<BR>Tim


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Sun 15, 2004 10:27 pm 
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Location: Mpls, Minnesota
Randy<P>Hope by now your 666 is up and running. After reading the posts by Lou and Tim I also remember having problems with the calibration pots shorting to ground.<P>Dave<P>------------------<BR>Intelligence is the ability to use your knowledge


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Sun 15, 2004 11:28 pm 
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Location: Grand Blanc, MI USA
Randy--I am not sure all of us understand the problem your tester has. I read your initial post to mean that, as you move the line adjust, the meter pointer will move below or above the line set mark--but cannot be set *to* the line set mark. <P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Mon 16, 2004 2:51 am 
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Location: Winnipeg, Manitoba, CANADA
What I had was a Line Adjust that would only take the needle from about the '20' to the '40' on the per cent scale. It just wouldn't get up to the '70', or the Line Adjust 'mark'. I checked everything, and changed the diode/capacitor twice. I even changed the resistor, keeping with 270K. I resoldered everything that couldn't outrun me. No change. Playing with the Line pot, and setting the filament voltage to say 6.3VAC for starters, the Line pot on 130 gave a filament voltage of maybe 5VAC, and setting the pot to 105 gave a filament voltage of just over 7VAC, so I thought everything was OK. I have three other 666's that I own, and I borrowed two others from friends. All plate/screen/etc. voltages checked with a few volts of each other. Setting the tester up to test a 7-pin tube, a 9-pin tube, and an octal; voltages and plate currents were within a small margin of each other. So, everything seemed normal, save the damned Line Adjust. <BR>This is where I took out the 270K resistor, and used a decade box. All kinds of resistors would let me get a 'high noon' Line Adjust reading, but to have the pot at center rotation meant a 15K resistor instead of 270K. I could have used 22K, 27K, 33K, 39K, even 47K. But that would have meant the calibration pot was at the extreme rotation. I wanted it centered, so I stuck with 15K. That seemed weird (like something was really loading the circuit down), but I put the 15K resistor in, and tested tubes all weekend. I left the tester plugged in all weekend as well. Nothing got warm, and everything seemed to compare with five(!) other 666's. It's a head scratcher, and I have no idea what happened. I've checked the meter movement with a power supply, and the swing is smooth enough. The last option I had thought of was to swap meters between two 666's. But I doubt that's it. As I say; all testers give similar quality readings, and all voltages/currents are close to each other. If there is a tough dog book for the Eico 666, I have a case that'll near the front.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Mon 16, 2004 3:23 am 
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Location: Grand Blanc, MI USA
OK--I certainly did not understand your initial post at all. If the tester delivers accurate results on a tube test, then the full scale current spec on the meter is likely correct. But--when you are doing the line adjust thing--it's the series resistance of the meter that is critical--since you are now measuring voltage--not current. It is possible that the meter is off spec and that the series resistance is far too high--this is supported by having to make that gross reduction in the one resistor value. Or--perhaps there is leakage somewhere in the line adjust circuit that is not allowing sufficient voltage to build during the line test. A simple meter swap would check for this. Or--hook up a digital meter to a good 666 and see what the mV reading is when the meter is reading half scale. Now compare that to what is going on with the problem tester. If the voltage is lower than on the good unit--it's a circuit problem--if it's as high or higher--then it's the meter. <P>I have been working on an Eico 667 today. The meter case is clear and I can see something I don't like much inside. The internal connections to the meter are not soldered at all--Just some type of spring connection. This is the type of thing that could cause high resistance and screw up the meter's series resistance spec.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Mon 16, 2004 1:56 pm 
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Randy,did you try checking the pot? They develope leakage to ground.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Mon 16, 2004 6:03 pm 
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Location: Winnipeg, Manitoba, CANADA
I did check the Line Adjust calibration pot for any resistance to the casing, but not the Line Adjust pot itself. I hope to get back at it right away, because I have some other avenues to explore (thanks!). I seem to have too many irons in too many fires, so I just try and dedicate at least a little time to an iron or two every day. Today I had planned to tackle a Stark high voltage power supply and a Heathkit O-10 (with no 'free' manual available). You can bet the outhouse neither will get completed today, but will make the 'someday' pile grow yet again.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Tue 17, 2004 2:52 am 
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Location: Grand Blanc, MI USA
Randy--see my last post on the Eico 667 for a possible clue to your line adjust problem.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Fri 20, 2004 2:02 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 420
Location: Winnipeg, Manitoba, CANADA
Ta Dah! Contrary to the opinion of a few ex-wives and countless therapists, I AM capable of accomplishing things other than pissing people off. <BR>I decided, just for something to do, to run every 666 I had 24-7 and measure everything that couldn't outrun me. I ran tubes in all of them, and checked Line Adjust', 'Leakage', and 'Merit' every fifteen minutes. The 'haunted' 666 still managed to have similar test voltages and currents. But the damn Line Adjust now drifted. What to do? Change BOTH 100K pots. Problem solved. The haunted 666 has been on now for nine hours since the new pots were put in. The Leakage and Line settings are rock solid. And the 'old' Line Adjust calibration series resistor is back!<BR>The power of prayer may work for SAT's and IRS audits, but not a haunted 666 (think about it). But the almighty 666 is STILL no match for a soldering iron operated with determination. <P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Fri 20, 2004 9:13 am 
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Location: Tokyo, Japan (2006~)
Congratulations ya Lizard!!<P>I too may be about 5 days away from my 666 problem being resolved... that's if I don't get sniped by someone who's got too many 666s that decides to get an extra meter for a rainy day, he, he, he... <BR> <IMG SRC="http://img.photobucket.com/albums/v297/angusx/990.gif"> <P>Chris<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Fri 20, 2004 7:51 pm 
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Location: Grand Blanc, MI USA
Congrats Randy--guess this was too obvious a problem for the rest of us to figure out. Were those calibration pots the wrong value? Strange that they would adjust at all if they were open or bad. Or--maybe they were open at the low end. I always spray the things with some Caig MCL. <P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Fri 20, 2004 11:32 pm 
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Chris, did my post not show up? I tried to say that's what happened on my unit and the pots were bad. I think these pots develop the "metal whiskers syndrome". They are hard to check out because they don't behave in a consistant manner. Sometimes a spray cleaner will help but the problem may come back as some particles will remain. Replacement is the best solution.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Sat 21, 2004 12:36 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Winnipeg, Manitoba, CANADA
It seems mine DID have whiskers; but at its' age, it's allowed. I had decided to waste today as well on this thing. I measure the pots; a little over 100K each. I opened them up, with nothing to lose. It seems the last owner sprayed Lord-knows-what in there, and the trace was very 'gummy'. So, I bathed the traces in methyl hydrate, and then cleaned them further with a good pencil eraser. Just for fun, I put them BACK in the 666. So far, the operation seems to work, but I think I'll eventually go back to new pots. We all know by now that this a malignant problem. It's was just short of a fun waste of a week; I should have pulled these pots a long time ago. But at least I know for the next 666 I get;-)<BR>Thanks for the tips. Now it's off to that 'some day' pile, and a few other goodies to get going. <P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Sat 21, 2004 1:26 am 
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Location: Grand Blanc, MI USA
Yes Lou--you are the Puzzle solver on this one. Sorry.<P>I only had that whisker problem once. It was on my wonderful RCA Master VoltOhmyst. The thing is like brand new--but would not work. Finally found the pots full of metal whiskers. Took all the pots apart, cleaned them and no further problems. That was about three years ago. The whisker problem was nearly impossible to find because the pot measured fine with a meter--but somehow when the unit was on and the pot energized, the whiskers would line up and short to the pot's metal case. I don't know what causes this problem--but is sure is not very common.<P>------------------<BR>


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 Post subject: Eico 666 Puzzle!
PostPosted: Aug Sat 21, 2004 3:27 am 
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Actually I think it was Alan Douglas that I first heard describe the problem. Usually I find I will solve a problem right before I am ready to give up. But then I hate to be defeated by a mere pile of wires and tubes. One thing that has become clear to me is never skip over a possible cause of the problem just because it seems improbable. Once had a radio with a low level hum which was caused by a mica cap soldered to the wrong pin of a tube. It was that way from the factory and I guess the owner thought it was normal and never had it fixed.<P>------------------<BR>


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