Sencore CR 7000 repair

[jeffilm]

I Have 2 Sencore CR 7000's that I purchased on ebay, neither work right. One displays no emissions (1 red bar only) on all guns. G1 and H-K shorts seem OK.The other displays false G1 shorts (low resistance) about 3 red bars into the gray cutoff area on the meter. Lo and high emissions in the same area on all guns. Blue gun sometimes erratic all the way into the green. Sencore No longer services these and has no service manuals. Lance at Choice Electronics has a repair/recalibrate service listed for CR 7000's I contacted him by phone last week and he told me He would check to see if his staff would work on these, his CRT tester guy had left him. Now I get no response from him all week. I was thinking of changing all the e-caps there are about a dozen. I would caution anyone from purchasing these on ebay. Most come from pawn shops. I don't think I've ever seen one connected to a CRT and have the display showing the emission. They are usually shown in the shorts mode. This will always give you a completely lit display, without a CRT connected which makes them say the unit is working OK. Does anyone have any Ideas??

[Polaraligned]

There are a lot of sellers that represent these as working. Stay away from the sellers who are selling as "untested".
If it is not working, and you purchased it as working, then E-bay is on your side.
Just file a claim that it is not as listed, and you will get a postage paid label to send it back and PayPal will credit your account.

Of course, this does not help you if you bought these as untested or it has been more than 30 days.

Matt over at ARF probably will be able to fix it, but it may not be cheap.

I don't think I would ever want one of these. My CR70 is not even my go-to tester. It is my older Sencore CR31. I have been using it for 20 years and I find the most consistent results with it.

[Username1]

I was wondering if those older sencore units were as good or better than the 70's,
and those 7000's are they just 70's with digital meters..? or a completely different
animal....? those 7000's must have been the last made.... were they sold at the same
time as the 70's ?

.

[MIPS]

I suspect it's just faulty logic.

[jeffilm]

Yes, I have not had much luck on ebay lately with electronics working. A lot of sellers throw away the power cords and say the units can't be tested. I think they know they are not working. Some of those old cords can't be found anywhere. One of the CR7000's was purchased almost a year ago, I just got around to using it now. Matt says he can repair theses. I sent them to him today. The price he quoted seemed very reasonable. I'll probably put one up for sale and take a loss. I will show it working with a CRT connected. Ya win some and Ya lose some. I'm still way ahead!. Thanks for the help

[rca2000]

I bought a pair of '70's..about 10 years back or so on ebay. The first one did NOT work...it will trip the power switch if it is on a grounded outlet. The second one DID work...and well. it IS my "go-to" tester. I like it BETTER than the 7000, with it's confusing bar graph display.

Still have that non-working one somewhere...I think the garage..

[Polaraligned]

My CR70 came from E-bay and did not work. It needed a new cutoff set potentiometer. No big deal. The CR70 is a serviceable unit and the schematic is readily available. I went looking for the CR7000 schematic on the internet and could not find it.

[Jon A.]

I guess I got lucky with my first CR70, except for the foam rubber disintegrating and covering everything in transport. Its only issue is the indicator sometimes drops into the bad zone when I switch to color tracking when the CRT tests fine otherwise. Moving the function knob back and forth gets it working again.

[Kevin Kuehn]

Originally Posted by Polaraligned

The CR70 is a serviceable unit and the schematic is readily available. I went looking for the CR7000 schematic on the internet and could not find it.

I'm curious where the CR70 schematic is available on the net? I got my very poor copy from Sencore, which is almost unlegible.

[bandersen]

I bought this CR70 service info on ebay. The scans are good quality and include schemtics, parts lists and PCB layout diagrams.

[drh4683]

I have both a CR-70 and CR-7000. I got lucky and got a good CR-7000 off ebay on the first try about 5 years ago. You may have bad lytics in your 7000. These were made in the late 90's and early 2000's which was that era of "bad caps" that was plaguing electronic equipment at the time.

But, like some have mentioned, I too like the CR-70 the best and is my "go-to" tester for most applications. I trust it's readings the most.
The CR-70 only has four adjustable grid bias settings. The CR-7000 has many more grid bias selections. However, I think the 70 is a bit more accurate. I think the CR-7000 makes some "good" tubes appear to be weaker than they really are which can potentially lead you to unnecessarily rejuvenating a CRT. This is because the set up specs on the 7000 require what I believe are excessively higher grid bias settings vs. that on the 70 for the same tube. Thus, the more grid bias you put on the tube, the less cathode current, thus a "lower" emission reading.

The 7000 does not have the 21" round screen test socket. You would have to use the "universal adapter" which is basically an adapter with individual clip leads so you can clip direct to the pins. The CR-70 has both "older" and "newer" versions. I spoke to a rep at Sencore a few years ago and they said the CR-70 was in production from 1982 thru 1996. If you want a CR-70 with the "#7" 21" round screen color tube socket, you need an older CR-70 unit built 1987 or older. The newer ones did not include that socket. Sockets are NLA through Sencore, but otherwise, many of the parts are still available through them.
The CR-7000 was introduced in 1997 and was in production thru 2006. It is much different electronically than the 70. It has a digital logic for rejuvenating tubes with timed pulses. This is to prevent cathode overheating and damage which works well and is effective. I do like the three LED bar graphs on the 7000. It is a nice instrument, but I still like the 70 best for working on the older sets. Nothing beats a good analog meter.

[jeffilm]

Matt was able to repair both units. One had a blown G1 regulator transistor. The other had a blown -12V regulator and 3 other IC's!!. I think most of these were used on video game monitor CRT's. Probably had the leads from the universal adapters short to B+ or didn't discharge the HV anodes. He said he never has seen any damage like this to these before.These are usually very trouble free (Thank God). There is protection built in, but there must have been extremely high voltage spikes to cause the damage. Particularly on the second unit. I tried them on three different crts and get the same results on both. Thanks for the help!!...Jeff