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 Post subject: Eico 667 Improvement
PostPosted: Aug Mon 16, 2004 9:54 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
While testing an Eico 667 today I noticed a tendency towards oscillation when two different 6550 tubes were in the tester. Moving my hand near the tube would lower the reading. Have seen a problem with 6DJ8's on other Eicos. On this tester I put ferrite beads on all the 9 leads that return to the push button switch board. This looks quite neat and totally cured the oscillation problem. The Svetlana 6550 reads a steady "90" now--and was off the scale before. Other tubes do not seem affected by the beads--probably took a really high current tube to cause a problem. The 6550 reading seems a bit low--then again the transformer is really humming and Eico might have depended upon a bit of oscillation to boost the readings--who knows. The bead trick is useful because there is great variation in the lead dress on kit built items. Poor lead dress will contribute to oscillation in tube testers--beads often cure the problem. <P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Aug Mon 16, 2004 10:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 30745
Location: Livermore, CA
Hi Chris<P> This is very common with Eico's on tubes with plate caps. Just holding the wire with a hand usually stops the oscillation. Your ferrite bead should also work on the top cap lead.<P>------------------<BR>Norm


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 Post subject: Eico 667 Improvement
PostPosted: Aug Tue 17, 2004 12:49 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
Just redid a second Eico 667 today, and it was wired much better with leads all close to the panel. Very slight tendency to oscillate with the 6550 and no need to mod with the beads. Tube tested at "90" just like the other 667.<P>Now--I did have to fool with the values of the resistors on the Line cal and Leakage cal pots with this tester--and reduce the values somewhat.<P>Plus--there was a wiring error on the two pots that I saw once before. The resistor is supposed to go to the wiper and one end of the pot. On this tester they forgot to jumper the wipers and ends of the pots together. This caused some odd problems on the last tester I saw wired this way. Could this be the problem with Randy's machine? <P>So today--two nicer than usual swap meet testers. Neither machine was close to working. Not that easy to fix either--due to wiring errors and missed/bad solder joints, three broken wires, and one messed up switch. Number of tube testers I have probably repaired now--400+. Number of testers that were working reasonably well when I got them--perhaps four or five. Not very good odds. So--don't any of you throw away tubes that test bad unless you know for sure that your tester is working. I just have this vision of millions of perfectly good tubes that were discarded because a messed up tube tester said they were bad.<P><P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Sep Sat 11, 2004 12:21 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 34
Location: LI, NY
Chris H<P>I just picked up an EICO 667 at a yard sale today, haven't powered it up yet. What do you check, look for, when you go through a tube tester?<P>Brian<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Sep Sat 11, 2004 3:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
You need to check all the resistors, clean all the controls, check for poor solder joints, check for broken wires, replace the caps and selenium rectifiers with 1N4007 diodes. Pay special attention to the grid pot--as these can be ruined if the tester is operated improperly. If all goes well (often not) you will be able to calibrate the unit per the manual instructions and have a good tester.<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Sep Sat 11, 2004 3:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Pocasset, Cape Cod, MA
Check the grid pot at the low end with an analog ohmmeter, for smooth operation. You can pry the back cap off the pot carefully, and see if the fibre form is charred.<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Dec Thu 30, 2004 3:49 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
Sounds like you are using a digital meter and picking up stay AC. These meters are so sensitive that just holding the leads in the air will provide a reading. Standard VOMs load a circuit and do not tend to produce such readings. This is not a result of the oscillation problem discussed earlier. Try putting a resistor--say 10K across the circuit where you are reading the AC--there may not be any to read then. The reason is that AC can be induced in the tester's wiring due to the tiny capacitance present. But--even though voltage is present--the amount of current is tiny. <BR><P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Dec Thu 30, 2004 9:54 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 410
Location: Tokyo, Japan (2006~)
Hi Chris H;<P>On your original post regarding placement of ferrite beads on all 9 leads, where exactly should I place the beads?? Could you please post a photo of how you did it?? I would like to do this on my 666 as I also notice some oscillations on 6550s and 6CA7s time to time.<P>Thanks in advance!!<P>------------------<BR>Chris M.<BR>Windy City USA


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 Post subject: Eico 667 Improvement
PostPosted: Dec Thu 30, 2004 3:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
BL: Did you replace the electrolytic filter cap involved in the transistor test? I never fooled with the transistor test--so really have no experience with the DC involved. The voltage may be poorly filtered and normally have a significant AC component--that is a possibility. Many circuits have both an AC and DC component--it all depends upon the amount of filtering after the rectifier.<P>Chris M: Can't post a photo because I don't have the tester anymore. Placed the beads where all the leads returned from the sockets to the push button switch board.<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Dec Thu 30, 2004 5:55 pm 
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Posts: 2253
Location: Howell, Mi
Hi Chris,<P>If my 667 calibrates per the manual instructions, can I assume this tester is OK? I don't have another tester to compare my results with. I checked all of the wiring, and it seems to be good.? I was cross eyed when I finished! I haven't yet recapped, checked resistors, cleaned pots, etc. Oh yeah, I won't forget the diodes across the meter! I'll do all of this some year....too much "stuff" going on now!<P>Thanks,<P>Greg<P>------------------<BR>"I have not failed. I have just found 10,000 ways that do not work."


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 Post subject: Eico 667 Improvement
PostPosted: Dec Thu 30, 2004 6:18 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 828
Location: Grand Blanc, MI USA
BL: The DC voltage in the leakage test is probably OK, and is filtered well enough for the intended purpose. If the test calibrates properly, and the meter is not bouncing around, the DC supply should be just fine. These types of DC circuits are not like B+ in an audio circuit, and even those circuits will have some small AC component. About the only way you are going to see "pure" DC is from a battery.<P>Greg: You need to complete the rebuild and calibrate. If some of the resistors are off--the tester might calibrate but deliver bogus results. The real test is how your unit tests actual tubes. If it finds the weak ones and the strong ones--then it's OK. Sometimes the voltages can be correct and the tester still misbehaves--that's why I started this thread. Things like the placement of wiring in the tester can have unanticipated results--like the oscillation that I mentioned in the beginning.<P><P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Jan Sun 09, 2005 1:24 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 11
Location: Ellensburg, WA, USA
One problem I have with my 666 is the 610A adapter pins don't make good contact in the 9-pin socket of the tester. They are clean, just seem to be a little short and don't always make good pressure contact.<P>I'm considering mounting the 610A permanently on the left side (so it'll be close enough for the plate cap wire...although I guess I could lengthen that) and hard wiring the umbilical cord through the chassis. Problem is I would want a connector inside for removal of the face when servicing. Any suggestions on a 9-pin connector?<P>Anyone else done this with ideas to share?<P>P.S. Also, I can't find any reference/use for the 'cap' peg on the 610A. Anyone enlighten me to it's ellusive presence???<P>Christopher KD7REM<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Jan Sun 09, 2005 7:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
You can get 9-pin "octal" connectors that are pretty decent. 9-pin Molex connectors look ugly but work well and are cheap. D connectors come in a 9-pin size (look on the back of your computer).<P>------------------<BR>


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 Post subject: Eico 667 Improvement
PostPosted: Jan Mon 10, 2005 12:48 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1982
Location: Oswego, NY, USA
Christopher,<BR>The add-on boxes (Eico 610, 610A, Coletronics B16, Precision G140, etc.)metal post is connected to pins #10, and to Compactron pin #12; your tester's cable clamp attaches to this pin. The sheets & ckt. diagrams are posted at "bama" & "Oldradio/Iglide" sites. <P>I sent to you an email with further information about design & parts. <P>Fred <P>------------------<BR>


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