HP 7970E Tape Drive Repair

My beloved monster HP 7970E vintage 9-track tape drive is not working anymore! It was fine working continuously during the two days of the VCF exhibition, but when I brought it home it would not load tape anymore. Time to look at the innards and find what is wrong.

[@LiveeviL6969]

When I used to work on old copiers, they use incandescent bulbs for some of the sensors and every time the machine was moved in or out of a building, it would break the filament. Had to carry bags of them just because of that. Good find!

[@77leelg]

Here is some hp trivia. Both the 7970 tape drive and 2631 printer were manufactured in Boise Idaho. The 7970 was the genesis of the Boise plant in the mid 70’s but both products came from what was called the Boise division of hp. The printer side eventually formed a partnership with Canon to make laser printers which became the genesis of the LaserJet printer products which are still the best selling in the world. I worked at the Boise plant for over 30 years and had a front row seat on an amazing journey. Those products were tanks like all hp products back then.

[@albinklein7680]

I have an old Grundig Radio-Alarm Clock with an ancient backlit LCD display for the clock/frequency display. Lit with a small halogen bulb. That bulb lasted exactly 35 years from 1985 to 2020. Continuously lit 24/7. Amazing.

[@Maxxarcade]

Those old machines were such a work of art, and that one is wonderfully clean inside! That's a great non-destructive hack as well.

[@bborkzilla]

Great thing for a Saturday with a cold: Watch CuriousMarc fix obsolete computers!

[@gooseknack]

True, but this tape drive is not obsolete, but outdated!

[@altamiradorable]

I repaired so many of those, the most occuring problem is the TAKEUP sensor ! Either the sensor or the board !

[@chriswatson2407]

That was a reel lightbulb moment

[@PRRGG1]

This video brought back great memories Marc. I was the supervisor for a 55kW UHF analog TV transmitter. Two Varian klystrons were employed in final service on an RCA TTU55. One afternoon the TV station went off the air. I had a co-worker with me and he couldn't understand why I walked into the transmitter room in the dark. The 480v three phase variacs in the focus supplies had a magnet current meter. Much like your tension arm, A #94 wheat bulb was used in the meter. When a magnet undercurrent or over current condition existed, the light beam was interrupted by the flag at the bottom of the indicating needle, turning off the 27kV DC supply to the klystrons anodes. GUESS what had burned out. In a dark room it was easy to spot and repair in the meter. Glad your LED hack worked, Curious Steve (me) would like to know if that LED is still working on your tape drive AND did you ever change the other lamp out during a PM cycle?

[@CuriousMarc]

Yes it still works and no I have not replaced the other lamp.

[@mrmstechtalks3752]

Oh wow - I never thought I would see one of these again. We had one with our Universities hp3000. I must have loaded hundreds of tapes on it during the mid eighties. At one point the motor got replaced. We kept the motor for arm curls.

[@paulkocyla1343]

Servos have something satisfying, seeing that smooth regulation :) I like that on the airplanes, too: When there is turbulence, the spoilers poke out quite aggressively, keeping it stable.

[@WaltonPete]

When you mentioned the optical sensor I just assumed it would be using some type of LED so you can imagine my surprise when you opened the sensor to reveal an incandescent bulb! No wonder it blew if you had to transport the drive in a vehicle to the exhibition - those filaments can be SO temperamental with vibration. Nice repair with the LED, I'd be tempted to change the other one as well but I expect you prefer originality over convenience.

[@ignaciomenendez5850]

What a fantastic narration of your repair Marc, congrats !

[@joseph9770]

Boy this sure gets my nostalgia pumping. One day I'm going to have a few vintage machines and a nice tape drive like your HP 7970. What a beautiful machine. Thanks for making these videos. :-)

[@DanielPalmans]

I LOVE your videos, it brings back so much memory. I work at hp since 1975. btw we use the same light bulbs in the 7900 disk head positionning. mechanism. The bulb was atomatically replaced every 3 months, among other stuff, during preventing maintenance :-)

[@dirtydon8661]

Just found your Channel. Love the vintage electronics! Hope to learn more electronics repair like logic troubleshooting with oscope..etc. thanks

[@aspirohk3558]

I really feel the burning desire to really get the internals of this, it looks so cool plus most are flooded with mac retro but this sounds great

[@zibobpompon5768]

It will be interesting to transform this beauty into an audio tape recorder and reader , the quality must be top range !!!!

[@MicrobyteAlan]

Good troubleshooting. I remember working on these old machines

[@MVVblog]

"It's always the last things you check that's wrong" this is why i always start from the end :-)

[@Kalumbatsch]

It's kind of trivially true, because when you've found it you stop checking :P

[@Blasserman]

Test points were needed because almost every kind of computer equipment was prone to failure back then. Using a lamp with a filament is a great example of why this was the case.

[@TheColinputer]

Ahh the wonderful days when stuff was designed to be repaired!

[@larrygall5831]

@ TheColinputer Yes, and they always had a schematic in the case or on the back of the machine. Nowadays you have to hope they're available online somewhere. There was also something about the printing that made old schematics much easier to read.

[@guitarpro248]

@@larrygall5831 agreed! I collect tube audio gear and all of it came with a service manual to be able to fix up the equipment! Even my JVC four channel has a schematic that came with it! It's a 4 page fold out schematic, but frightening enough to make me scared to dig into it to find out why my left channel is dead 🤣🤣🤣

[@kevinmiller4486]

I remember replacing those bulbs. These were fun to align if you replaced the head. Lots of test bds and oscope used to get it in peak form.

[@hpguy136]

wow memories -- if that's the drive I think it is, I worked in the same lab as the 7970 guys back in the early 80's -- have any HP 2608A impact printers? We did real quality work at HP Boise.

[@RinoaL]

very good job! when it comes to electrical troubleshooting i find it far more confusing than mechanical troubleshooting.

[@Lennyp4]

those OG Mudbone caps in the corner: 🗿 Marc: 😳👉

[@michaelberry1028]

As an HP CE I repaired many 7970’s, one of my customer sites was the Shell computer centre in Manchester UK. They had many of the variable density model as they took in tapes of all types from across the Country, the drives were part of a Microfiche printing system for long term storage of data. On PM visits the drives had to be calibrated from 800 to 1600 BPI.

[@CuriousMarc]

I'd kill to get a dual density model...

[@chrislimbert4757]

YAY! It works again!!

[@CosmicWizard79]

Great vid, keep them coming :)

[@MoraFermi]

It would be fun to have a drive like that with modern write head and tape formulation.

[@NicheAsQuiche]

Imagine LTO7 on a tape that big

[@tmichiels]

I feel guilty as being a kid in 90s taking these apart for parts like the transformer, the caps and the motors for just experimenting purposes. I still have parts of these in my attic...

[@suchness18]

:D Great repair video!

[@DoRC]

Was there a variable opening slit in the arm that varied the light coming through or some kind of gradiant material?

[@CuriousMarc]

Much more clever. A constant width but spiral-cut slit, in front of a photoresistor with two terminals (+ and ground) and a midpoint tap (position sense). The equivalent of a voltage divider controlled by two photoresistors. Depending of the ratio of illumination of the two halves you get a different midpoint voltage. If the slit is towards the top, the midpoint voltage is higher, if its at the bottom, the midpoint voltage is lower.

[@stupossibleify]

I'm thinking you really should find an incandescent bulb to replace that LED sometime, but perhaps not if you intend to keep moving it around.

[@timlipinski2571]

With the LEDs it should out last the rest of the tape drive. Back in the good old days before LEDs you kept extra bulbs for your flashlight (and batteries) ! Thank you for the video ! tjl

[@nealelliott]

wow, I wonder how old that incandescent bulb was? a led replacement is such a better option. nice work!

[@bobl78]

that´s when tape drives needed regular maintenance to change the oil, filters and bulbs

[@ntoobe]

Awesome repair to watch! [1:57] You've got the small lathe there?

[@drakethedragon457]

There are some massive filtering capacitors in the PSU

[@glasstronic]

Very cool! I'm surprised that that lamp gave-up the ghost, given the derating; should'a gone for 20 years continuously lit...might it have become gassy? ;-)

[@stupossibleify]

The hazards of moving old, highly sensitive equipment around. But it is important to showcase such important and beautiful kit

[@DandyDon1]

I guess then that the very aged and rather fragile incandescent lamp source finally gave during travel after the show. At least it happened afterward and not before or during. This time Murphy's law did not prevail?

[@Jenny_Digital]

That 'Vintage bulb' you saved, looks like one I regularly replace on our machine light guards at work. What are it's dimensions?

[@CuriousMarc]

Absolutely. It's a "garden variety" 6V bulb, 5 mm in diameter. Still made today and easily available.

[@Lethaltail]

It had festival fever!

[@JEMHull-gf9el]

That LED is to new take it out! LOL, J/k

[@markusjacobi-piepenbrink9795]

WOW!

[@guitarpro248]

I love at 12:09 the lights dim from all the power being used 🤣🤣🤣 they're like my tube amplifiers, inefficient, but fun to use! Cheers!

[@leisergeist]

And to think I was grumbling about having to manually fix a DC100 tape after my HP85 ate it (why? pfft, who knows) Now I realize I'd hate to have to mess with reel to reels lol

[@Veso266]

would you be able to play and hear Audio real on this one?

[@benjaminpountney5457]

0:59 LOOK AT DOZE CAPACITORS! DEY HUGE!

[@htroberts]

yeah, I noticed those as well. I’d like to know what values they are, and the ratings on those motors...

[@RonLaws]

I wonder why they didn't use LEDs originally, were the types available back then just too dim to be useful in such an application?

[@CuriousMarc]

This design is quite old. The first version of this tape unit came out in 1970 (the HP 7970A, which has identical mechanics). So these sensors arms must have been designed in 1968-69. I suspect LEDs were just too new, dim and expensive to be considered. Their simple solution was to use a cheap 6V light bulb, but severely under voltage it so it would last a very long time.

[@RonLaws]

Ah yes, that makes sense, LEDs were quite pricy back then, and only useful for indication.

[@cnvogel]

Also old LEDs were very inefficient, just barely lit when run at 20mA (where a moden high-efficience LED will be eye-scorchingly bright). And old LEDs definitely are aging, I have some vintage audio gear where constantly lit indicators are now really, really dim to the point where they are barely discernible under normal desk light, so even if they had used the first available LEDs in the 70s I guess they would have worked not as long as the 6V lightbulbs did.

[@DandyDon1]

In my digging and a reference to something I remembered. Was the first practical LED display calculator introduced by HP in 1972, the HP-35 with it's itsy-bitsy display equipment with coke-bottle magnifying glasses?

[@AiOinc1]

+Christian Vogel I've got a laptop with dim charging and power lights - it's been on the charger most of its life I presume. Original battery is still good, though. It's not an old laptop either, it's a Toshiba Satellite A135-S4427.

[@rsuryase]

How many MB of data can a reel hold?

[@rapsod1911]

Can you publish schematics?

[@mglmouser]

:-( I want a vacuum column tape reader

[@bradleymorgan8223]

how much data does that tape reel store?

[@RaymondHng]

bradley morgan At 1600 bytes per inch, a ten-inch reel holding 2400 feet of tape would store about 50 megabytes data. At 6250 BPI, 250 MB of data. A 64 GB flash drive today will hold 256 reels of those tapes.

[@jtveg]

The element must;'ve broken during transportation.

[@user-gr5do8nk7e]

1:04 that's beautiful !

[@warp9988]

What is the lifetime and current age of the enormous electrolytics inside these things?

[@muholovmuholov8265]

People like you have to put the monuments!

[@TymexComputing]

5000 years later: as we can see these leds are not functional, i need to find a matching magic infrared light source to fix my beautiful HP 7970 or better i will use an active artificial light sensor with a camera that works on the infrared energy that is already present in the enclosure - no need to match the power rail.

[@skizzofly]

A Rat on the backround at 11:03 ? ps good job

[@AiOinc1]

5:54 oh god are those wax capacitors?

[@cnvogel]

From the looks of it, pretty standard axial foil capacitor in a potted plastic housing. This is not a tube/valve radio :-).

[@AiOinc1]

Christian Vogel Thank god. Those caps short like crazy, some 80% failure rate for me. Those capacitors have been used in a few computers as well - it just looked like this was one of them.

[@htroberts]

why not just replace the lamp?

[@CuriousMarc]

Just convenience, I did not have one at the ready (nor did I know what model it was).

[@guitarpro248]

Back when equipment was made to be serviced! What a great era for electronics! I work on vacuum tube audio, and even those were made to be serviced! Imagine all the stupid lawsuits now about letting customers work on gear that has 350 VDC inside! Now everything is meant to be thrown away... SAD