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Author Topic: technics rs 1500 speed problem UPDATE AND THANK YOU FOR THE FEEDBACK!  (Read 3367 times)

Offline analogfan

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Hello all,

I picked up a cherry 1500 (at least cosmetically), that runs slow on all speeds.  I can adjust the speed manually and it locks-in pretty well with just a bit of drift when 1st turned on.  If I leave the machine on and the capstan motor running for a couple of hours (use a rubber band to hold down the idlers) it will lock-in manually with virtually no drift - when I take it off manual, it runs slow at all speeds.  Any ideas?

Also, the tape lifters do not operate when tape is loaded (fast forward and rewind).  If I remove the tape and cheat the system by holding the idler down, the lifters work, but intermittently.  There seems to be dirty contacts in the right-hand idler assembly as sometimes I have to work it up and down to stop FF or reverse when I have things cheated (no tape loaded).  Also, any ideas?

The machine had been unused but otherwise well cared for.  Pots were noisy but worked them all manually 25 - 30 times as well as all of the front panel switches.  Sounds great on phones and operates well otherwise.  Tape transport controls and tape handling is otherwise excellent.  Brakes seem fine.  I have degaussed the heads, cleaned everything in the tape path with alcohol well, washed the rubber idlers rollers down with water - they seem to make good contact and do not appear to be slipping.  The heads are in excellent shape.   

I have not pulled it apart yet or used Deoxit on contacts or switches but probably will, given age of the machine and fact it saw little use.   

Otherwise, she is a beautiful thing!

Thank you in advance for any ideas/suggestions.  Regards, Bob

UPDATE UPDATE UPDATE UPDATE UPDATE:

I have had the 1500  on for several days in a warm environment with the tensioners cheated and running at various speeds.  Continued to work all of the mechanical parts and the lifter problem has resolved itself.  BTW, I think the unit has been stored in a home environment and it does not have any bad odors or signs of abuse, smells good in fact, no signs of rust, and the more she runs, the better she plays and operates mechanically.

The speed issue persists however.  She locks in well with the manual speed control with little/no drift.  Still runs slow when the pitch/ manual control is out of the system.

I have both of the service manuals, a dual trace scope, a digital volt meter and a frequency counter.  Does anyone know of a source for the calibration tapes or a source that has the equipment to creat those required?  BTW, the 2nd volume of the service manual is EXCELLENT for the Technics 1500/1506!  I have to put a plug in for HiFi Engine where I obtained them!

I had an OTARI B3 and the alignment procedures were nowhere near as clear!

Thank you all for the support and suggestions!

RE: Tape Project mods for the Technics RS series - are any of the tape path mods available for a handy DIY guy like me?

Thanks again, appreciate your time and skills!  Bob Edwards
« Last Edit: January 25, 2011, 06:21:15 PM by analogfan »

Offline mikkelbreiler

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Re: technics rs 1500 speed problem and tape lifter problem
« Reply #1 on: January 21, 2011, 08:06:13 PM »
Hello all,

I picked up a cherry 1500 (at least cosmetically), that runs slow on all speeds.  I can adjust the speed manually and it locks-in pretty well with just a bit of drift when 1st turned on.  If I leave the machine on and the capstan motor running for a couple of hours (use a rubber band to hold down the idlers) it will lock-in manually with virtually no drift - when I take it off manual, it runs slow at all speeds.  Any ideas?

Also, the tape lifters do not operate when tape is loaded (fast forward and rewind).  If I remove the tape and cheat the system by holding the idler down, the lifters work, but intermittently.  There seems to be dirty contacts in the right-hand idler assembly as sometimes I have to work it up and down to stop FF or reverse when I have things cheated (no tape loaded).  Also, any ideas?
I'd listen go for all the solenoid switches. Could be simple corrosion and build-up on switches and contacts. Also the tape lifters should engage, listen to the sounds when you engage play. Softly put a finger on the back of the tape on the tape lifter and engage play, do you feel anything? If there is sound of engagement from the mechanism it may be the lubrication dried up in storage, you'll have to take the mechanisms apart and clean them out and replace the lubricant. I cannot tell what to use but no doubt the regulars can recommend a suitable lubricant common where you are. I never had this type of problem. But you never know with units from storage, the time it was stored and under what conditions.

Quote
The machine had been unused but otherwise well cared for.  Pots were noisy but worked them all manually 25 - 30 times as well as all of the front panel switches.  Sounds great on phones and operates well otherwise.  Tape transport controls and tape handling is otherwise excellent.  Brakes seem fine.  I have degaussed the heads, cleaned everything in the tape path with alcohol well, washed the rubber idlers rollers down with water - they seem to make good contact and do not appear to be slipping.  The heads are in excellent shape.   

I have not pulled it apart yet or used Deoxit on contacts or switches but probably will, given age of the machine and fact it saw little use.
Rubber parts made it so the rest of the deck could also have escaped storage fairly well. But sometimes a little moisture can wreck an electrical item, while rubber parts are usable.

Your mileage will probably vary based on your preliminary findings. But unless you find odd smells, tons of rusty parts, signs of tampering - like cable ties undone but done redone or loose screws - I'd say it is worth keeping and working on it.

Long term and periodic storage doesn't really matter. It is what happens in storage that counts the most. If you do not know aboutthe actul storage, you can hope for minimal damage and have accept some mor ethan that. If you expected maximum damage you should not have invested in it other than for visibly usable parts. Various states of repairs will be OK provided the cost of acquisition is matching the work expected to be done. One should always make thoughts for repairs of worst case when buying an old electrical item. At some point it is no longer economically feasible.
Short periods of freezing is not good, and so is heat, moisture, spills, but if you spilled something and you did everything to remove it there could years later be an issue where you could not clean up or missed liquid.

I do not think electronics of that age are more resilient I think that as technology comes in smaller and smaller packages a single drop of water is more deadly to an iPhone circuit than a 70s tape deck. Chances are the drop would not even short anything out, let alone leave a desposit nearly a component. On a pcb in a mobile phone several components are touching the space a single drop of water will cover.

Also the iPod was not made capable of lasting as long as your tape deck. Not even with maintenance. Modern electronics is not designed for maintenance only for cheap repairs (read: pcb swapping) under warranty.

-Mikkel

Offline docb

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Re: technics rs 1500 speed problem and tape lifter problem
« Reply #2 on: January 21, 2011, 10:24:58 PM »
I would suggest doing the pinch roller pressure, brake tension, motor control and tape tension adjustments per the service manual. You need a good tension gauge (preferably one with a telltale) that goes up to 1000 grams for the brake and roller pressure, a scope for the motor control adjustment and you really need a tentelometer to do the tape tension adjustment as well as possible, but you can use the voltage test points in the manual to get pretty close.

IIRC the tape lifter height is somewhat affected by adjustment of the pinch roller positioning mechanism. Been a while since I've been inside a 1500 (Shawn does all the tape machine mods these days) but I think maybe you have to pull the capstan motor to adjust that stuff.

Also check to see if the bellows behind the tension roller arms are cracked or split. You should hear a puffing sound as you work each tension roller arm up and down.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: technics rs 1500 speed problem and tape lifter problem
« Reply #3 on: January 22, 2011, 02:11:22 AM »
Hey Bob,

Lots of excellent suggestions ( the ones that Doc gave have the added benefit that those are items that should be done with any machine when you first get it).
It could be that Mikkel hit the nail on the head though. It could very well be that someone spilled something into the machine. The reason I say that is the tensioners (idler) and the solenoid that controls the lifters are toward the top of the machine (directly under the vents) and neither are the sources of common problems with the RS15xx series.

The first thing you should do is get the service manuals (2 volumes).
Once you have the manuals, take off the back and top of the machine. Nothing tricky here, just screws.
Since you're having speed issues, turn the capstan flywheel by hand. It should turn "like budda" continue spinning and stop after rocking back and forth a bit once or twice.
Turn on the machine with the tensioners "fooled" so the capstan will run. Listen closely for any weird noises (many of these machines have a ticking sound which seems to come from a wavy spring washer that "preloads" the bearing but this is normal).
While your at it, put the machine in play (with no tape still) and observe. Both reel tables should turn (the supply reel will slow after a few seconds) but the reel motors should "whirr" smoothly. Release the tensioners to stop the machine then repeat with ff and rewind. (btw, they'll turn in opposite directions to apply tension on the imaginary tape)

Reach around the machine and turn the reversing roller. There's a thin belt connected to it that turns a white pulley which turns another tiny belt which operates the tape counter. The reversing roller has a little more resistance but it shouldn't be excessive.
The speed adjustment pot and/or the speed selection switch can sometimes result in weird speed problems. Try working it back and forth about 20 times and see if it helps. A little squirt of contact cleaner in the back of them before doing this can help.

Regarding the lifters,.. first, be sure that the lifters themselves aren't sticking on the headblock. They get real close so any damage to them could make one stick.
After checking that, there's a section of the manual that addresses the pinch roller pressure/stopper. Remove the stopper and move the plunger in and out. If it sticks, clean and put a bit of grease on the plunger.
Adjust the pinch roller pressure and be sure that the rollers are contacting the capstan at the same instant (a good trick to check this is to once again fool the machine so the capstans turning so when the rollers make contact the start to turn).
Hopefully, you can take care of the lifters this way since you do need to remove the capstan motor and transformer to do any further adjustments.

Of course, the symptoms you describe could be part of a larger problem. For instance, if the caps in your power supply are dying, it could be throwing off the tension balance of the reel motors which could keep the lifters from moving out and the voltage could be too low to operate the speed controllers properly.

So, those are some things off the top of my head that you can try. No mater how you look at it though, the stuff that Doc suggested need to be done after any of my suggestions so bear that in mind. The service manual is essential!

steve koto
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