488 Mk I motor noise - what is normal?

[Pennine Lad]

Hi folks

I have recently bought a 488 Mk I stated fully serviced. The motor to my ears when switched on not in use seems distractingly noisy and wondered what is normal. Even more so if adjust the Pitch. Measured 44 dB on iPhone 'db meter' app peaking at 50 dB with Pitch not at max.

Have owned the 414 in past which was not quiet but was hoping going up the range would be better.

Would be interested to hear of any quantified noise measurements eg using a phone app of their own example to judge if this is in spec or not, if not can it be improved, thanks!

David

 

[SkywaveTDR]

Hi David, I work on these decks and I don't know what motor noise you are describing- are you meaning the capstan motor or the Mode motor? The reel motor may be a different thing. In some models the mode motor were made with nylon rear bearings and these as all plastics do break down in time. I have replaced some motors on 122 Mk II decks with a better mode motor with brass bearings front and back but the screw hoes do not meet up as most these motors are 11mm wide mounting instead of 10mm and the screw holes are not 2.6mm screws but 3mm and they can not be too long. This then leads me into a whole collection of 3mm x4mm or 5mm length screws and washers and I have with some drilling to expand holes been successful in repairing these decks that should last a lot longer than these plastic motor parts- this noise would only be heard at transport change times. Further in these deck that use a mode motor with belt this can also be a source of noise if it is slipping or the belt has a crack in it. So what are you hearing specifically? This is where I would go in and take the transport out to find out what the noise is all about or where it is from. I have repaired a dozen of these in the past few years but a lot of Mk II due to bad Gear C conditions.

 

[Pennine Lad]

Hi

Many thanks for your insightful reply. It is the motor that spools up when switch on and whose speed changes with pitch control so presumably the capstan motor.

Not having had this model before uncertain what is normal noise.

Thanks,
David

 

[SkywaveTDR]

I have worked on these and in my work did not ever notice a noise from motor other that maybe a dry bearing which is resolved by AMS oil being allowed to soak in as the motor faces upward. Once AMS oil get in the motor will turn very smoothly. Electrical noise might be cause by first the lack of proper case grounding- that is the reason for that black wire affixed with the screw to the metal mechanism. I have forgotten this wire in other deck 1 or 2 times but I know what I get when I forget it so the fix is pretty fast. There have been a few cases that this motor will need to be replaced and that with third party motors these days might require some modification of circuits but I do get the units to work.

 

[Pennine Lad]

Hi

Many thanks for your help and advice and will explore the motor lubrication / grounding.

David

 

[SkywaveTDR]

As to the noise - in units I have worked on and I have two or three of those here now, I do not hear any motor noise either mechanically produced or from electronic interference. That is just my experience so it is possible with some assembly methods that noise might be experienced as no two technician do the same kind of work.

 

[Pennine Lad]

If you have a moment sometime it would be interesting if you could quantify with a phone app dB meter held next to the closed cassette tray when not in use. So just measuring the capstan motor noise. Thanks.

David

 

[SkywaveTDR]

I am really not a fan of smart phones and their apps. I still have a 3G phone and there is no noise to measure that I could hear anyway.

 

[Pennine Lad]

No problem, thanks again for your insights which are valuable.

David