Beomaster 8000: The Recap Continues

I continued recapping the Beomaster 8000 that sits on my bench right now. I rebuilt the filter and tone control PCB that sits underneath the control panel, the two tuner PCBs, and the preamplifier board. As usual, I used quality Japanese 105C capacitors. I also cleaned all board connectors with a fiberglass brush to remove oxides, and then I coated them with DeoxIT D100L to protect them from future decay. Here are some pictures of the boards before and after:

Filter and tone control PCB before:

and after:

Tuner boards before:

and after:

and a detail shot:

And the preamplifier board before:

and after:

and a detail shot:

On to the main reservoir caps for the outputs! 

Beomaster 8000: 3D Printed Control Panel Linkage

This is the continuation of an earlier blog entry at http://beolover.blogspot.com/2014/06/beomaster-8000-3d-printed-controls-lid.html

I started reassembling the recently recapped Beomaster 8000. It was time to try out the 3D printed control panel cover linkage that I had printed a few weeks ago after finding that the original linkage had cracked and lost one of its hooks. 

I put in the 3D printed part (Makerbot II, PLA, highest density), and it worked nicely - for a few openings and closings - then it popped out at the damper. This meant that my part had a slightly too wide gap on that end, which would allow the damper arm to come loose. I redesigned the part in Inventor with a 0.2 mm smaller gap, and had it printed again. This time it worked very well. The part clicked in solidly, almost too tight. I lubricated it with Ballistol, which resulted in very smooth operation. 

I made a short YouTube video that gives some more info and shows the part installed and in action:

The STL file for the linkage is posted on my website at beolover.com:(http://beolover.weebly.com/control-panel-cover-linkage.html).

Beomaster 8000: PCB 1 and 2 (Tuner) Recapping

Today was Tuner Day of the current Beomaster 8000 restoration project. The tuner worked basically fine, but there was an intermittency on the right channel, seemingly depending on the moon phase...;-). Tracing the signal with the oscilloscope, revealed immediately that one of the contacts in plug P6 was poor. I pulled the boards apart (they come out together...), and cleaned the contacts with a fiberglass pen and bent them a bit for added contact pressure. Then I added a coat of DeoxIT D100. As usual, this seemed to do the trick. Wiggling the boards did not cause problems in the right channel anymore! Here is a pic of the contacts before cleaning...some black oxide spots are clearly visible where the female headers made contact:

Such black spots come easily off when using a fiberglass pen on them. I forgot to take a picture, but one can achieve as-new looks that way. The DeoxIT further cleans the contacts and provides a protective layer against future oxidation.

While the boards were out, I also recapped them with quality 105C caps. An uneventful procedure. Here is a picture of the boards before the procedure:

And after:

And a detail shot of the region around the IF stage (CA3189E):

Well, almost done!! On to the preamp board (PCB #3)...

Beomaster 8000: Rebuilding the Filter and Tone Controls Board (PCB #4)

Today I took the filter and tone controls PCB of the Beomaster 8000 out and replaced the capacitors. This required unsoldering the signal strength meter leads from the PCB, and unscrewing the plastic panel that holds the switches, buttons and sliders. Here is a pic from the bottom of the PCB before taking it out:

The meter in the lower left corner needs to be unsoldered to be able to remove the PCB from the plastic cover. Five screws hold the PCB to the plastic cover. It is important that these screws do not get tightened too much when re-installing the board. The plastic standoffs can easily crack.

Here is a photo of the meter after unsoldering the leads:

This is a pic of the board after removing it before replacing the capacitors:

And with new caps:

Several of them needed to be tilted to accommodate for the low clearance between the plastic cover and the board. This PCB also had one cracked ceramic capacitor (C207).

I replaced it with a new 10nF type:

After screwing the plastic cover back on (it is a bit difficult to get all the buttons and sliders slotted at the same time - patience helps...;-) I soldered the meter leads back onto the board, and tested the Beomaster...seems all works fine. On to the tuner boards.

Beomaster 8000: 3D Printed Controls Lid Linkage

I just received a 3D printed part for the Beomaster 8000 I am currently restoring. When it arrived I pressed "Programming" to access the controls, and the brushed aluminum cover popped open at an alarming speed, indicating that the damper was disconnected. Once opened the Beomaster up, this was confirmed. Sadly the plexiglass link lost its bottom end and therefore lost contact to the damper that prevents the cover from snapping open. Here is a picture of this sad state of affairs:

So I recently drew up this part in Autodesk Inventor, guesstimating the missing bottom end (I didn't have another 8000 open at that point to take measurements of a complete part). Then I had it 3D printed on a Makerbot II using black PLA: Here is the result:

I designed the holes a bit smaller, and then drilled them out with a 9/64 (right, lid) and a 11/64 (left, damper end) bit. The Makerbot has a hard time to get hole dimensions perfect on this size scale, and it is better to drill the material carefully to get a more machined feel for rotating joints like in this case.

I tested the part on the damper and the lid joints, and it seems to click into place fairly well...when I assemble the Beomaster again, we will see if this really worked (I am a bit concerned that it might disconnect from a joint when using the cover in a routine fashion - I will post an update on that).

Anyway,my fun with 3D printing continues!