Very early Motorola VT71 scored - Videokarma.org TV - Video

bandersen · #1 07-14-2011, 01:02 AM

I just picked up this set tonight. It's a Motorola VT71 with what I believe is the very first run of the chassis TS-4.
It has a 7F8 osc/mixer and two large metal 0.3 mfd @ 6000 volt caps mounted on the chassis. It also has channel #1

Overall it's in quite good condition. The bottom cover is there with all the metal caps over the adjustment holes. It has the metal back, all the knobs, plastic faceplate is in very good shape. The only problems are a few veneer chips and the usual melted CRT mask. I actually had that large veneer chip in my hand when I picked up the set, but can't find it now

Hopefully, it will turn up.

Looks like it was at a garage sale and everyone passed on it.
The masking tape is really stuck on there good. Does anyone have any tricks for getting it off without damaging the finish ?

Could this really be the 2,425th VT71 to roll of the line ?

The channel selector on these sets only has 8 positions.

You always get 1, 2 and 7.

The dealer would configure the other five (3/4, 5/6, 8/9, 10/11, 12/13) for your area.

bandersen · #2 07-14-2011, 01:07 AM

Here's a peek at the inside.

I really hope these are originals and not an ugly repair job.

There's the 7F8 up towards the front. Later sets used a 12AT7.

Ah, those caps do appear on the tube chart so I bet they are original.
Weird. The earliest schematic I could dig up is the the TS-4B and it doesn't have these.

That's all for now. I'll try to find time tomorrow to pop the chassis out and test the 7JP4.

ChrisW6ATV · #3 07-14-2011, 01:11 AM

Very nice. Both of my VT-71s are TS-4Ds, I think, and both have channel 1 and no fine-tuning control.

bandersen · #4 07-14-2011, 01:30 AM

Cool. I didn't realize they had so many revisions with channel 1 and no fine tuning. The oldest I have is a TS-4H with fine tuning.

I just noticed the hum adjustment in the bottom cover. That's something else I don't see on the TS-4B schematic

Electronic M · #5 07-14-2011, 01:31 AM

Wow! I've never seen such a primative version of that chassis before.

bandersen · #6 07-14-2011, 01:34 AM

Aw nuts, I checked in the Riders index and this chassis appears to be covered in volume 1 which I don't have

bandersen · #7 07-14-2011, 01:42 AM

I found a scanned copy of Riders vol1 TS-4 chassis at the ETF. It appears that this is the TS-4 "late" version which uses a 6AL5 and 6SQ7 in the audio circuit. The TS-4 "early" uses a 6S8GT.
I was hoping it was the very first version, but it's still pretty darn early

Red Raster · #8 07-14-2011, 03:05 AM

Nice find, Early and unique and hope a good crt sweetens the deal.
Wow! the crt is connected using individual wires with sockets pushed on the pins of the crt base.

AndrewM · #9 07-14-2011, 05:00 AM

Nice little Motorola, shame we don't have early sets like these where I live.

I find turpentine useful for softening the adhesive on masking tape so that it can be removed. It doesn't harm most finishes but it would be wise to check first.

Sandy G · #10 07-14-2011, 05:13 AM

Seems like SOMEBODY was making "replacement" masks for these-I THINK I've seen 'em on The E Place.. Every one of these I've seen has had that problem...

Zenith26kc20 · #11 07-14-2011, 09:08 AM

My Motorola book has the 7F8 schematic but the 6KV caps are large tubulars under the chassis but not in the usual place. Those don't appear to be oil caps. That's the first time I noticed no fine tuning. That must have driven the owner a bit nuts as drift occured during warmup. My Sears B/W has a number of 7F8's also. LOVE the CRT connectors!
Can't wait to hear of the progress on this one!

VintagePC · #12 07-14-2011, 09:12 AM

Quote:

Originally Posted by AndrewM

Nice little Motorola, shame we don't have early sets like these where I live.

I find turpentine useful for softening the adhesive on masking tape so that it can be removed. It doesn't harm most finishes but it would be wise to check first.

If you don't want to risk turpentine, use Windex or glass cleaner with a bit of ammonia in it. That stuff will eat smoker's tar off of painted finishes, but be prepared with an old rag and a bit of elbow work to get the gummy bits off.

Masking tape is a PITA to remove unless it's been applied within the last day or so.

IsthmusTV · #13 07-14-2011, 10:26 AM

Nice find, Bob! I've also has some success using WD-40 to remove masking tape adhesive (particularly the petrified variety). I let it soak for an hour or two and then gently scrape with my thumb nail.

Good luck with the restoration!

-Clark

***Eric H*** · #14 07-14-2011, 10:54 AM

Re: Masking Tape, Naptha, a.k.a Lighter fluid should take it off without damaging the finish.
Squirt it on, let it soak a while and scrape it off with a credit card or some other non metal scraper.
I use this all the time to take old tape and stickers off of record labels.

***Eric H*** · #15 07-14-2011, 10:59 AM

Wow, I just noticed the 6kv caps mounted above the chassis!
Never seen that before either.

I have a channel one VT-71 with no fine tuning and I don't think it has those either, I'll have to take a look.

That has to be a very early one.
I wonder if they moved those caps because they found out having 6KV above the chassis was a bad idea?