Adjusting Ferrograph supply reel tension - UK Vintage Radio Repair and Restoration Discussion Forum

Phil G4SPZ · 1st Dec 2011, 12:24 am

I have two mono Ferrographs, a 631 and a 633. The left-hand supply reel tension on the 633 is much tighter than on the 631, and produces flutter towards the end of a spool of tape. Is there a relatively easy mechanical adjustment to correct this, please?

I've searched the Forum but can't find this topic being aired previously. Thanks for any advice.

Phil

TIMTAPE · 1st Dec 2011, 1:04 am

Sounds like either the brakes are sticking on, or the bearings in the motor need an oil. I think the plain bronze bearings at top and bottom of the reel motors have a small felt disc to retain the oil.

BillDWVA · 1st Dec 2011, 3:25 pm

If the brake on the supply reel is not sticking - as suggested - it is worth checking that the resistor that is shunted across the left reel motor during playback and record is OK and is actually in circuit. In theory, during play and record modes, both take-up and supply reel motors are placed in series and the supply side motor is shunted to give a torque differential. If the wiring, switch contacts or resistor were open circuit then the back torque would be increased. It is a wirewound resistor mounted off the chassis and should be noticeably hot whilst running. Sorry but I do not have a circuit diagram to hand to give you the circuit reference or value, as I write this.
Hope this helps, Bill.

Phil G4SPZ · 4th Dec 2011, 6:31 pm

All sorted now.

It turns out that, on the model 633 deck the left-hand reel has two brakes, one main brake which is held off in playback and fast wind, plus a second brake which appears to be there simply to apply tension to the supply reel. This second brake is also released in play or fast wind, but is held at all times against the spindle by a light spring. The only means of adjustment seems to be by stretching the coils on the spring, which I have done and the problem has been completely cured.

I also have a model 631, on which the supply reel tension is applied by reverse motor torque in the 'conventional' manner.

It would be interesting to know why Wright and Weare made such a design change between the two models - energy efficiency, perhaps?

1st Dec 2011, 12:24 am	#1
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Adjusting Ferrograph supply reel tension I have two mono Ferrographs, a 631 and a 633. The left-hand supply reel tension on the 633 is much tighter than on the 631, and produces flutter towards the end of a spool of tape. Is there a relatively easy mechanical adjustment to correct this, please? I've searched the Forum but can't find this topic being aired previously. Thanks for any advice. Phil __________________ Phil Optimist [n]: One who is not in possession of the full facts

1st Dec 2011, 1:04 am	#2
TIMTAPE Octode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 1,969	Re: Adjusting Ferrograph supply reel tension Sounds like either the brakes are sticking on, or the bearings in the motor need an oil. I think the plain bronze bearings at top and bottom of the reel motors have a small felt disc to retain the oil.

1st Dec 2011, 3:25 pm	#3
BillDWVA Pentode Join Date: Nov 2010 Location: Tenby, Pembrokeshire, Wales, UK. Posts: 139	Re: Adjusting Ferrograph supply reel tension If the brake on the supply reel is not sticking - as suggested - it is worth checking that the resistor that is shunted across the left reel motor during playback and record is OK and is actually in circuit. In theory, during play and record modes, both take-up and supply reel motors are placed in series and the supply side motor is shunted to give a torque differential. If the wiring, switch contacts or resistor were open circuit then the back torque would be increased. It is a wirewound resistor mounted off the chassis and should be noticeably hot whilst running. Sorry but I do not have a circuit diagram to hand to give you the circuit reference or value, as I write this. Hope this helps, Bill.

4th Dec 2011, 6:31 pm	#4
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Adjusting Ferrograph supply reel tension All sorted now. It turns out that, on the model 633 deck the left-hand reel has two brakes, one main brake which is held off in playback and fast wind, plus a second brake which appears to be there simply to apply tension to the supply reel. This second brake is also released in play or fast wind, but is held at all times against the spindle by a light spring. The only means of adjustment seems to be by stretching the coils on the spring, which I have done and the problem has been completely cured. I also have a model 631, on which the supply reel tension is applied by reverse motor torque in the 'conventional' manner. It would be interesting to know why Wright and Weare made such a design change between the two models - energy efficiency, perhaps? __________________ Phil Optimist [n]: One who is not in possession of the full facts Last edited by Phil G4SPZ; 4th Dec 2011 at 6:34 pm. Reason: Removal of repeated words