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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 21st Jun 2020, 2:20 pm   #1
Whaam68
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Join Date: Feb 2007
Location: Luton, Bedfordshire, UK.
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Default Harting HM8

Perhaps foolishly being a reel to reel neophyte I recently purchased this deck from an advert on the forum. Mainly because I liked its looks and thought it would look nice with my green era valve Heathkit amp and Cotswold speakers.

I am unable to locate a service manual or schematic anywhere for this deck so I first went through the electronics lifting leads, testing and where necessary replacing caps like for like Before applying any power as this deck is date stamped Nov 59. The main smoothing can and the larger electrolytics actually tested ok For capacitance and esr on the modern tester and for capacitance and leakage at working voltage on the hunts bridge. All other caps were massively out of tolerance or leaky and were changed

This done I applied power through a lamp limiter and all seems ok...even the magic eye recording level meter seems strong.

Ok switch on the take up reel and The capstan thingy next to the heads both spin strongly....which I’m assuming is a good thing!

Rewind was working but faded off....then what I’ve found is if you hold the rewind key down 2/3 of its travel it is strong and fast....but once fully engaged it stops rewinding completely.

Fast forward isn’t working.

I’m attaching some pics ...the rewind Key moves a metal pulley over Via levers to press the main drive belt onto the supply reel “drum”....you can see the metal pulley near the brass coloured spigot in the pic. Any ideas why it rewinds well on 2/3 of a key press then stops as the button is fully engaged? Is there usually a way to adjust the tension as it seems the metal drum is pressing the drive belt too hard on the drum turning it into a brake!

On the ff side it looks like a rubber idler moves into place to drive the take up reel drum. You can just see it between the two wires in the pic. Im going to try roughing this up and applying rubber restorer and cleaning up the drum with alcohol.

I’m very out of my depth on this one but would like to get it working again. The heavy duty belts seem basically ok having some stretch left.

Once this is sorted I’ll move onto testing the output.

Mike
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Old 21st Jun 2020, 7:57 pm   #2
Whaam68
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Default Re: Harting HM8

Having just looked at this again there is play in some of the belts. I’m going to try that first.
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Old 21st Jun 2020, 8:59 pm   #3
DMcMahon
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Default Re: Harting HM8

Hi Mike,

A very nice looking R2R, looks to be in good condition especially for its age, does seem to be a rare make/model.

Sounds like you are doing all the right actions. Does seem strange about the 2/3 key press, would not expect normally any sort of required adjustment for the RWD key. You will have to try and work out what is the difference between the 2/3 key press and the full key press (engaged) to see what the difference is in how it positions the drive idler, and see if any way of adjusting it.

From the photos and your description somewhat difficult to fully understand the actual drive mechanical operations, nothing like getting ones hands on to really understand how it works fully. The drive belt being driven hard onto the drum does not sound correct.

David
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Old 22nd Jun 2020, 6:57 am   #4
Whaam68
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Default Re: Harting HM8

Thanks David
The main drive belt is a very thick round section composed of soft rubber (like a soft hoover belt).and I’m wondering if it’s expanded slightly with the rubber restorer I’ve liberally applied reducing the clearance. This belt runs in a machined channel In a big aluminium flywheel underneath the take up reel and in rewind a metal idler is pushed by a lever onto the half round of the exposed belt at the top of the channel to drive the flywheel. It’s as if on full RW travel the metal “idler” now presses so hard on the belt into the channel that it acts as a brake on the flywheel. At least that’s what seems to be happening. It looks like if I pull the motor I should be able to access the belts which is my next move. It is a bit of a nightmare to work on as the mechanism is well hidden under the deck top plate.
Regards
Mike
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Old 22nd Jun 2020, 9:49 am   #5
DMcMahon
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Default Re: Harting HM8

Mike,

I never heard of rubber restorer being used on drive belts, I think normally applied to idler wheels and maybe other rubber components. The belt does look large. Good luck.

David
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