HMV 102 maintenance.

[anchorman]

Hi Mike,

That is interesting info. I just checked a screw chart again, and it does appear that UNF 4-48 would be ver close.

I will check and see if that works. Unfortunately I don’t have a way to compare thread angles, but I should be able to check with a nut. It would surely be helpful if it were such a thread as I already have taps for this size.

I’ve always thought an optical thread comparator would be a nice tool to have, but don’t imagine I’ll ever find one at a reasonable price, and for as rare as I actually need one, I could not justify ownership of such a thing. I imagine they’re like boats, and it’s much better to have a friend with one, than to own one yourself

[anchorman]

I believe the safest and quickest way to tell the thread of a screw is to find a matching nut.

Also, if the hole had strength enough to strip the thread of the screw in that way, I don't think an extra nut is necessary. Is the hole stripped at all? Possibly the screw was inserted at a wrong angle at the factory and the hole is still OK.

Other screws don’t insert easily, so there’s either part of the screw left behind, or the hole is damaged somehow. Hopefully it just needs chasing with a tap, once I find the appropriate tap to use!

[soundgen]

Hi Mike,

That is interesting info. I just checked a screw chart again, and it does appear that UNF 4-48 would be ver close.

I will check and see if that works. Unfortunately I don’t have a way to compare thread angles, but I should be able to check with a nut. It would surely be helpful if it were such a thread as I already have taps for this size.

I’ve always thought an optical thread comparator would be a nice tool to have, but don’t imagine I’ll ever find one at a reasonable price, and for as rare as I actually need one, I could not justify ownership of such a thing. I imagine they’re like boats, and it’s much better to have a friend with one, than to own one yourself

Yes that's how I first found HMV threads were UNC or UNF we had an old hardware store in Bedford Goldings sadly now gone after 150 years they had an optical thread comparator and it was so easy to get a match to any thread I wonder who has it now ?

[soundgen]

Hi Mike,

That is interesting info. I just checked a screw chart again, and it does appear that UNF 4-48 would be ver close.

I will check and see if that works. Unfortunately I don’t have a way to compare thread angles, but I should be able to check with a nut. It would surely be helpful if it were such a thread as I already have taps for this size.

I’ve always thought an optical thread comparator would be a nice tool to have, but don’t imagine I’ll ever find one at a reasonable price, and for as rare as I actually need one, I could not justify ownership of such a thing. I imagine they’re like boats, and it’s much better to have a friend with one, than to own one yourself

Yes that's how I first found HMV threads were UNC or UNF we had an old hardware store in Bedford Goldings sadly now gone after 150 years they had an optical thread comparator and it was so easy to get a match to any thread I wonder who has it now ? And they stocked UNC and UNF taps and dies

[anchorman]

Pleased to report that I finally got around to finishing servicing this beautiful machine. New graphite grease in the spring barrel, everything cleaned and oiled and gear teeth greased.

The threads that were damaged were easily chased with a 4-48 tap, and now all I’m missing is the screw that was damaged. I’ll figure something out with it eventually.

The tone arm is oiled and adjusted properly, and I managed to free up the reproducer and get it adjusted better. It seemed that the needle bar was over-tight, or possibly just extra dirty at the pivots. It moves much better now, and seems loose enough, but not so loose that it rattles side to side. Sounds much better.

I like my Columbia 112a, but this machine is so much nicer to use.

My only issue is a bit of a rattle from the governor, I think. Only audible when the platter is running free. As soon as there is a little bit of a load from the needle on the record the rumble goes away. I adjusted end play on the governor shaft, but I think the gear driving the worm gear is slightly too low. Is there an adjustment for the spindle shaft other than shimming with a washer under the shaft at the pivot? I’m wondering if there was something that got lost in taking the motor apart, or was missing already?

[Phono48]

Is there an adjustment for the spindle shaft other than shimming with a washer under the shaft at the pivot? I’m wondering if there was something that got lost in taking the motor apart, or was missing already?

There is no adjustment, and putting a washer under the shaft will prevent the end of the shaft touching the ball bearing that should be in the socket, located in the removable bottom plate. Check that the ball bearing is there, as it often drops out as the bottom plate is removed. If it is not there , then that may be the cause of your problem.

Barry

[anchorman]

No ball bearing! I looked for one when I took it apart, but didn’t see it. Wasn’t sure if there was supposed to be one or not, but at the time was thinking there should be one. I was told it should be 3/32” diameter. Easy enough to source another.

[Inigo]

That will do the trick. These are easily lost without notice if you didn't expect it to be there... It happened to me also the first time with these motors.

[anchorman]

well, it turns out there was/is a ball bearing. 3/32" diameter as was suggested to be correct. it was in there with some grease, and now all is clean again, and verified that the bearing is there.

The question is now, why the gear wheel sits so low on the worm gear. and whether a larger bearing would be the appropriate way to solve the problem. There is a small indent in the bottom of the brass bushing that holds the ball bearing, and perhaps this has gotten worn over the years? I can fit either a 7/64 or ⅛" bearing ball in there to raise the height a bit. but then there would be slightly different contact of that indent, which may cause more wear over time. It doesn't appear that the governor shaft ends are offset and adjustable (except for axial play) as they are on the columbia/garrard motors that I've seen.

I need to inspect also to see if perhaps there is a way to press the bushing slightly higher in the motor bottom plate. I doubt there is an easy way to do this, however!

Any thoughts on the best approach to fixing this would be most welcome!

[anchorman]

it looks like an ⅛" ball is slightly too much, it pushes the spindle gear a little bit above the center line of the worm gear. 7/64" I don't have at the moment, so cannot try that out. 3/32" is slightly below the centerline.

Important questions: is there some reason why the gear should be below the center line of the worm gear? Or should it be as close to centered as possible? I believe the noise issue that I was having was a result of the end play being a little bit too much. That ought to be minimized once the endplay is correct. Still would like to have the height of the spindle gear in the optimum position on the worm gear if that is possible!

it seems like the optimal design from a maintenance standpoint would have a small set screw in the bottom of the bushing that has a detent for the ball to ride in, and would allow the height of the spindle gear to be adjusted as needed. but surely wasn't cost effective in practice.