A simple mod for the later H-K turntables

[Mawerick]

It should be on the data plate on the back. The ones sold thru the Military shops in Europe should be dual voltage and possibly have a Euro-standard plug as does my Army PX sold ST-7.

Unfortunately it's a US model. I think I'll dig out the old T60 and part it out, see if I can fit the power board from it into the T55.

 

[Pio1980]

What's with your T60? If you do part it out PM me.
The service manual for the T55C and T60C show an alternate dual voltage power trafo for what they call the "general" model version, the T60 does not. The power requirement for them is so slight, ca 10W, that the smallest step-down trafo/autoformer would be more than sufficient and the trafo could be salvaged from almost any older dual voltage piece of junk with an iron core trafo of at least 20W power consumption rating.

 

[Mawerick]

It was basically a parts unit to begin with, but also got pretty banged up during shipping, seller had left the platter in place etc. so the damage was rather extensive.

I'll retrieve it from my folks garage during easter.

 

[wlmill]

After reading this thread, I might have to consider getting a belt drive turntable. I have always been sensitive to speed variations. I listened to the needle drop that was posted earlier and I don't think speed variations would be a problem with H-K turntables. It is hard for me to imagine finding a turntable that sounds better than my current turntable, but I know it is possible. I have researched newer turntables and it is hard to find one that has low wow and flutter specs. I am not saying they are not out there, I just haven't found one yet.

 

[Ilikevinyl]

Did you change anything other than what you mentioned that could affect the highlighted item?

My HK T55C is my backup turntable so it sits on top of my closet. I take it out from time to time to run it. This last time I took it out the motor only ran for 2-3 seconds after I moved the arm to the start position. I didn't do anything to the turntable. I never had any problems with it in the past.

My main turntable is a Thorens TD-160/SME 3009 arm. And my other turntable is a Technics SL-1650 which I use for stacking 7" 45rpm records.

 

[Pio1980]

I'm guessing that your TT needs the electrolytic capacitors replaced for starters then. The motor switching system is basically a latching circuit that engages when the power is switched on and the activated end-of-play autolift circuit unlatches the motor power circuit, stopping the motor. Either something is unlatching the thing or the latch isn't holding. I'm just too thickheaded at present to analyze the ckt deeply enuff to suggest something more specific other than to suggest C201 and C202 may be the capacitors most likely to affect this ckt if defective..

 

[Ilikevinyl]

I'm guessing that your TT needs the electrolytic capacitors replaced for starters then. The motor switching system is basically a latching circuit that engages when the power is switched on and the autolift unlatches the circuit, stopping the motor. Either something is unlatching the thing or the latch isn't holding. I'm just too thickheaded at present to analyze the ckt deeply enuff to suggest something more specific other than to suggest C201 and C202 may be the capacitors most likely to affect this ckt if defective..

Thank You so much for the advise, I'll look into that.:thmbsp:

 

[Russellc]

Ummm no. The spring has to go into its resonate frequency when energy is imparted into the spring. The spring should drop energy (acoustic/mecahnical)down to (depending on spring rate/mass load/etc) 2 1/2 hz to about 4 hz. That frequncey then gets turned to heat as the mass the spring is trying to push up at its frequency rate is spent. cramming the spings full of foam turns the spring into the resonate frequencey of the foam materal. There should only be enough damping material in the spring to control the jounce time.

Agreed...there is an excellent site I have book marked on my home computer,
I think there is a link to it on the Vinylnirvana site about suspension adjustments and it spells out quite clearly that these foam should be removed and why. They were installed by the factory to "help" with floor steps skipping the table, but they dont work....moreover they tend to short circuit the springs intended function. The AR springs are too small anyway, get the extended threaded studs and Linn springs for a nice improvement.

Russellc

 

[Gravelyguy]

Pio1980 and Marcmorin,

Thanks for for all your thoughts on the t60. I did the mods described in post 1 to my t60 yesterday and all I can say is "Oh my". It took what I thought was a very nice sounding table to another level. My 13 year old daughter said it best listening to some Brubeck. "Dad, you can hear every individual note so clearly." She is a budding drummer and really liked the understated cymbal playing on side one of Time Out that went from kind of muffled to sharp and clear.

If you guys have any other tweaks that that us novices can manage, I am all ears!

Thanks again,


Dave

 

[Pio1980]

Thank you for reporting your observations, AFAIK you are the first to try it since I first posted this. The TT is a pretty solid concept and execution with the exception of that rigid but rather lively substructure and the belly pan, drying up their resonances can only make it even better. I don't have much else to offer at this time as they got almost everything else mostly right and that's all one can ask from good overall balanced design.
BTW, some sources recommend a 25.0 belt and this is too tight, a 25.7 would be preferable. Better looser than tighter. Another thread on another BD TT discussed pre-starting the platter with a push-turn and I'd recommend that with these to take start-up stress off the motor commutator and brushes for longer service life.

 

[Pio1980]

The tombstone digi sounds different in this TT than any other I've put it in, rather than sounding a bit thin and 'technical' it has tremendous dynamics with a full-bodied midrange and highs more in proportion with the rest of the range. If it had a generic sound in the other TTs it does not have it here, sounds like a totally different and more costly cart. I'm also hearing details in familiar material I don't recall from previous auditioning but not in the analytically detailed sense, more due to a rendering of dynamic shading/ proportion within the soundfield that more clearly opens the tambral and textural character of individual sonic events without evening them out. This set-up loves well recorded live ensemble content, listening to the Jussi Bjoerling Swedish recital recordings it's very obvious when different date takes were used, not so much thru other turntable set-ups. The dynamics of his powerful voice come thru here wide-open unrestricted. With lesser recordings it does its best to play what's there but does nothing to euphonically tart them up and they can sound less familiar and satisfying as a result than thru a TT that perks them up as some do.

 

[marcmorin]

The tombstone digi sounds different in this TT than any other I've put it in, rather than sounding a bit thin and 'technical' it has tremendous dynamics with a full-bodied midrange and highs more in proportion with the rest of the range. If it had a generic sound in the other TTs it does not have it here, sounds like a totally different and more costly cart. I'm also hearing details in familiar material I don't recall from previous auditioning but not in the analytically detailed sense, more due to a rendering of dynamic proportion within the soundfield that more clearly opens the tambral and textural character of individual sonic events without evening them out. This set-up loves well recorded live ensemble content, listening to the Jussi Bjoerling Swedish recital recordings it's very obvious when different date takes were used, not so much thru other turntable set-ups. The dynamics of his powerful voice come thru here wide-open unrestricted. With lesser recordings it does its best to play what's there but does nothing to euphonically tart them up and they can sound less familiar and satisfying as a result than thru a TT that perks them up as some do.

Pio, that is a very good explaination of the term "organic" sounding. Dynamic range is more than how loud something can get from its most quiet part. The micro dynamics of why a note sounds the way it does, or the character in the human voice, or hearing the back of the note with as much detail as the front of the note to me is much more important in playback. I also find the tables that easiest portray that type of soundfield are suspended belt drives with rigid coupling between the arm and spindle bearing. A continual loop to drain energy. The new Rega tables with the addition of a metal skeleton embedded into the plinth between arm and bearing attest what others have known for a long time. Glad you're hearing the magic.

 

[Mawerick]

Ok now, I managed to replace the power board + transformer on the T55C with parts I took from the old T60. It was an EU model after all. The T55C now works fine @ 230V.

I also did some modifications along the lines in post #1, except I used a piece of sound proofing bitumen between the counterweight and subchassis. Also put a large piece of the same stuff on the bottom plate and some smaller pieces along the subchassis. Didn't touch the springs though, they still had their original fabric wrap in place.

Everything seems to be in order now

Needledrop, same take as I posted earlier but this is with the modified table: The Wall. Again a very large file.

 

[Pio1980]

If bitumen is what is also known as tar it wouldn't be appropriately effective for this application if it acts as an adhesive for the weight, the mass weight has to float somewhat freely to damp the primary upper-midbass resonance but not too loose in order to damp the higher frequency resonances and harmonics as well. If checked before mod, tapping either the rim of the platter away from the arm or the end of the arm mount will produce a low-frequency resonance in the substructure that can be easily felt on the fingertips at the arm mount or platter edge. The mounting screws with the felts under the washers and weight should be tightened just to the point that the weight is still readily moveable but not floppy-loose. Then the tap-test with the mat and record weight in place as before should produce no LF resonance if it's right. If the bitumen sheet you used does this and continues to work right then go with it and please get back to us with a sound result report.

 

[Pio1980]

A word about the stocker OEM hard mat. A straight-edge across the mounted mat will show it slightly dished with a raised outer portion. This means that the record weight will flatten out slightly warped records as would a reflex clamp, a good thing. The hard mat behaves much like a hard plastic mat or platter, a deliberate design decision.
I would really like to know who designed this TT, so many better TT design features for reasonable money on a really solid build. The only things they missed was using the substructure compensation mass plug as a resonance damper and damping the belly pan cover.

 

[muzy]

As I owen a 35c and not a 65c as it apears you have. I am still folowing what your are doing to see if I can use any tweeks on mine. Regetably I have nothing to contribute. Thanks Pio1980.
Glen

 

[Mawerick]

If the bitumen sheet you used does this and continues to work right then go with it and please get back to us with a sound result report.

I was somewhat incorrect earlier on, it's not actually bitumen but butyl rubber compound designed for sound deadening and vibration damping. It's not acting as adhesive since the other side is covered with aluminum foil. I tightened the counterweight screws by fingers just enough so that the weight isn't loose but can be moved.

I'm hearing things from familiar records that I never knew were there. Amazing.

 

[Pio1980]

I was somewhat incorrect earlier on, it's not actually bitumen but butyl rubber compound designed for sound deadening and vibration damping. It's not acting as adhesive since the other side is covered with aluminum foil. I tightened the counterweight screws by fingers just enough so that the weight isn't loose but can be moved.

I'm hearing things from familiar records that I never knew were there. Amazing.

I am very pleased to have helped make your listening experience really better rather than just different for so little effort and outlay. Enjoy!

 

[Pio1980]

Pio1980 and Marcmorin,

Thanks for for all your thoughts on the t60. I did the mods described in post 1 to my t60 yesterday and all I can say is "Oh my". It took what I thought was a very nice sounding table to another level. My 13 year old daughter said it best listening to some Brubeck. "Dad, you can hear every individual note so clearly." She is a budding drummer and really liked the understated cymbal playing on side one of Time Out that went from kind of muffled to sharp and clear.

If you guys have any other tweaks that that us novices can manage, I am all ears!

Thanks again,


Dave

Hey Dave & Group!
I have pretty much finished with the TT portion as posted, the arm has my attention now. Low-mass arms are always theoretically and practically problematical in the sense that they do not reaction mass-load the carts to direct all the sonic energy into the generator which ultimately affects dynamics, and the vibration termination/control at/ into the pillar can be poor to non-existent with these arms. This arm doesn't do the former any better or worse than any other arm with a composite cart mount and that can't really be changed or fixed here so we are stuck with it. The pivot gimbal section while not bad is somewhat lively which can be heard thru a stethoscope. Since re-engineering the arm is out of the question the most practical course of remediation is to fashion a broad spectrum damper for the gimbal to tame the ringing resonances to further the systems sonic neutrality and detail resolving ability. Fortunately ITO supplied a suitable damper mounting in the optimal position and I have a couple prototype ideas I need to try that can be fabricated by most ingenious users from more-or-less common readily found objects and material. The idea I like now would use the carcass of a clear-bodied disposable lighter and tiny glass beads or filtered dust-free fine sand. I have fabricated one and will try it out and get back to the group. One add'l comment, this version won't fit under the closed dust cover if bonded on, the thinner Buss fuse box version will.

 

[Pio1980]

Making this as simple as possible, obtain a plastic 35mm film can and fill it ca 1/2-3/4 full with clean dry dust-free sand, aquarium sand would be good. Set it centered atop the ITO gimbal tongue (you do remove the dust cover to play your H-K, right?) and spin a few of your fave well-known albums and get back to me.