[hcraig244]

The tone arm cover has lost a securing tab at some point in its life, the residue of superglue can still be seen on whats left of the tab…cleaned it up and re-attached it using Aleenes tacky glue, strong enough to hold it be easily removed when required

• This reply was modified 2 months, 3 weeks ago by hcraig244.

Attachments:

You must be logged in to view attached files.

[hcraig244]

As the deck I’m currently working on had undergone a re-cap we only sourced service kits for the other two, which now leaves us short of a 0.47uf  63v cap….I have in my stock a 0.47uf 100v cap that I will use for the next deck, I know that Martin frowns on such a selection suggesting that the capacitor gets “lazy” due to operating well below its capability….however 63v is also well above the operating voltage in this case so i think i can justify its use….comments always welcome ;¬)

[hcraig244]

Changed out the 47uf for the prescribed 0.47uf and its made a massive difference, not surprising as the 47uf is 100 times greater than it should be, reading up it acts as an integrator or filtering element. It smoothes out the signal coming from the tracking sensor before it triggers the operational amplifier to drive the carriage motor. Because the capacity is 100 times larger than specified, the circuit’s RC time constant  is elongated by a factor of 100. The tracking error signal must build up over a much longer duration (approx. 10 platter turns) before the voltage crosses the threshold required to activate the motor. All according to AI….every days a school day!

 

• This reply was modified 2 months, 3 weeks ago by hcraig244.

Attachments:

You must be logged in to view attached files.

[hcraig244]

Starting to give the main PCB a looking at and I’ve noticed C4 in the tracking circuit has a value of 47uf as opposed to the prescribed 0.47uf. The manual and the capacitor kit from martin both identify o.47uf, to be honest I’m not sure exactly what effect this will be having….but its coming out.

 

• This reply was modified 2 months, 3 weeks ago by hcraig244.

Attachments:

You must be logged in to view attached files.

[hcraig244]

Therefore….I have an electrical issue going on in the main PCB or Control Panel….I will check all the power supplies first off and make sure I have steady 5v and 15v supplies, also have a good look at what capacitors where fitted when it was re capped along with the solder connections on each, any advice will be appreciated (Mark….I’ looking at you) ;¬)

I’m thinking back on this from when I replaced the control panel << and >> adjusted the LDR adjusting screws and managed to get them both to around 560mv (should be around 600 to 700) so we’ll see…..it may be due to slightly different LDR’s fitted? however when I operated << and >> everything worked fine….so I’m calling this a win!

Could this be associated with the issue? looks like a separate circuit to me ??

[hcraig244]

Having cleaned the worm screw/bushing and rails with IPA I was confident I didn’t have an issue with sticky drive components….new sensor lamp and LDR rules them out. So as I have another two machines that, as far as I know, are working fine I tested one out with a disc in place and stylus inserted and to my delight found that this set has a transport Carriage that turns every rotation of the platter, well almost….probably every 2-3 on average.

This established I removed all the mechanical parts (everything that sits on the chassis), leaving the main PCB/Control Panel and power transformer in the case, and installed the same parts from the fully functional deck….powered up and found I was getting the same issue as before….this eliminates all the mechanical components.

To be sure I installed all the rogue mechanical parts  into the fully functional case and with a very slight adjustment of the tracking sensor shutter got everything working fine, transport motor rotating approx every 2-3 rotations of the platter

 

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

Ok

All back together and time to set up the carriage transport sensitivity, however hard I have tried I cannot get the motor to drive even close to every rotation of the platter!…its doing nothing for around 10 rotations then turning too many times, its almost like its on/off control rather than proportional control! Gave up and opened a bottle of wine and considered the issue over a barbeque in the garden ;¬)

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

This allowed me to remove and replace the lamp and LDR a lot more comfortably…….just need to re install the board and re-solder the wires….

Attachments:

You must be logged in to view attached files.

[hcraig244]

However despite the dismantling above I felt it was too difficult to try and remove the lamp and LDR in situ, not to mention soldering in the new components so i unsoldered the very fine connection wires and removed the small circuit board.

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

Fortunately Beolover posted a blog detailing how to get to it which was a great help, lots of dismantling going on

 

• This reply was modified 2 months, 3 weeks ago by hcraig244.
• This reply was modified 2 months, 3 weeks ago by hcraig244.

Attachments:

You must be logged in to view attached files.

[hcraig244]

Ok

Parts have arrived from Martin and the exercise can go on removal of the carriage travel lamp isn’t easy

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

Great news….particularly around the archive posts….so much knowledge and pictures contained therin

Craig

[hcraig244]

Ok….received 2 cartridges in the post, fitted one and balanced the tone arm to neutral then set it to 1.0 gram. With the platter drive connections unplugged I hit play….tone arm moved to the correct position and dropped…however the carriage refused to move forward when nudged inward…hit stop and the tone arm moved back to rest.

My view is that the tracking sensor lamp (like the << and >> manual operators) and possibly the LDR too has passed its/their best, tried again and this time measured the voltage to the lamp 14.68vdc…so good, concentrated on the adjustment screw and had some success….after several adjustments managed to get the unit to play over halfway through an album at which point it decided to stop and return to rest…did this a couple of times despite a number of attempts at adjusting the shutter….looks like everything else is functioning correctly however the lamp and as it will be exposed the LDR too will need replacing….the carriage isn’t moving forward every 2 or 3 rotations of the platter but will move forward after around 9 0r 10 rotations…clearly not good.

• This reply was modified 3 months, 1 week ago by hcraig244.

Attachments:

You must be logged in to view attached files.

[hcraig244]

Mark

Thanks for the detailed explanation above, your bang on with the LDR / Aperture Sensor Drift in the Control Panel being responsible for the issue….and following replacement of the lamp and both LDR’s (changed them out as I was in there anyway) as detailed above, the set appears to be working fine. I still need to set the carriage travel sensitivity, as I have disturbed the original setting during the work carried out, will need a cartridge fitting to complete this…..watch this space ;¬)

Craig

[hcraig244]

Belt replaced with new one and re-assembly commenced, had to think about this as its a while since I took it apart ;¬)

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

Replaced the lamp box cover and connected the control box up…powered up and with a disc on the platted hit start, everything operated correctly, the platter spun, tone arm moved the drop position, and it dropped onto the disc, with no cartridge so I hit pause and the tonearm lifted and waited for the next instruction..,,I adjusted the LDR adjusting screws and managed to get them both to around 560mv (should be around 600 to 700) so we’ll see…..it may be due to slightly different LDR’s fitted? however when I operated >> and << everything worked fine….so I’m calling this a win!

Just need to replace the carriage drive belt on this, replace the double sided tape on the wayward panels, set the carriage travel sensitivity once we have a cartridge fitted and this is done (famous last words I know)

Attachments:

You must be logged in to view attached files.

[hcraig244]

Separated the control panel PCB from the pushbuttons and de-soldered the two LDR’s and the lamp, soldered in the new components…the new LDR’s are smaller than the originals however I’m confident they will function correctly.

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

New components have arrived….decided to replace the lamp and both LDR’s

 

Attachments:

You must be logged in to view attached files.

[hcraig244]

Lampbox cover back off…..the voltages at P5 pins 4 and 6  840mv  and 630mv respectively….and the pickup moved nicely across the platter and returned to rest….looking good.

New lamp and photo cells is my conclusion…unless anyone has anything to add? maybe replace the lamp alone would be enough?

Craig

[hcraig244]

Lamp box cover back on, adjustment screws would all the way out and could not get the voltages at P5 pins 4 and 6 below 1,5v and 960mv respectively…and the pick up moved its usual 2cm and actually did wander very slowly further in…

Attachments:

You must be logged in to view attached files.

[Author]

Posts