Beogram 4000: Replacing the Reservoir and Motor Phase Capacitors

I completed the recap of the Beogram 4000 on my bench by replacing the reservoir and the motor phase capacitor. I recently developed a 3D printed adapter for that, which secures the new smaller capacitors in the location of the old ones using the original mounting strap. This post gives more detail about the replacement process and a detailed 'wire map' of all the connections that go to these capacitors. It can get a bit confusing when doing this for the first time. Here are a few impressions from this particular Beogram 4000:

This shows the original cans:

This is the replacement assembly with the new capacitors placed into the 3D printed adapter. This shows how to prepare the capacitors to accept the wiring. Note that the two capacitors on the left are the replacement for the unipolar original 150 uF motor capacitor. I use two 300uF caps back to back:

And here is a shot of the installed assembly:

Like all the parts that I develop, this is assembly is available as a kit to other enthusiasts. Just send me an email.

Beogram 4000: Replacing the Electrolytic Capacitors on the PCBs

While I worked on the breakout board needed to replace the RPM relay with a modern encapsulated signal relay, I also recapped the PCBs. I think it is worthwhile to replace these vintage electrolytic capacitors since the tantalum types can actually catch fire when they go, while the orange aluminum caps are often out of spec at this age. I usually use quality 105C grade capacitors from major Japanese manufacturers, good for another 40 years...;-)

Here are a few impressions:

This is the main board in original condition:

And here after replacing the capacitors (the RPM relay is still in there):

The power supply PCB also has two electrolytic capacitors. This shows the original board:

And here after the replacement:

All good now in the capacitor department! Here is a picture of the lovely old color coded tantalum capacitors. I wish they would make them still that colorful!

Ain't they pretty?? This is Beolove...;-). On to the reservoir caps.

Beogram 4000: Replacement of a Stuck RPM Relay with a Modern Encapsulated SMD Relay

The Beogram 4000 that I am currently restoring was not able to switch the AC motor to 45 RPM. After replacing the incandescent light bulbs in the control panel it became clear that, while the 45 RPM button would properly illuminate the 45 trimmer pot, the motor would not change its speed. I traced the signal, and it turned out that the relay was broken. The relay simply switches different resistor networks into the feedback of the Wien oscillator thereby changing its resonance frequency.

The issue with replacing vintage relays is that modern units usually are much smaller and also have a more standardized footprint. This vintage relay actually has an unusual pinout in that the two throws are not mirrored across the relay like in modern units, but are different. The translation between modern and vintage relays was made with a breakout board that matches the pinout of the original relay.

I made a short video about this process. It explains the circuit and gives a demo of the new relay click. This is important in my opinion, due to need to get an audible feedback when pressing one of the RPM buttons. All other buttons give a direct mechanical feedback, i.e. this seemed important. Here is the video:

Here are a couple high res shots of the breakout board. Front:

And back:

This design drops directly into the solder points of the original relay.

Fisher X-100 Valve Amplifier in the House!

Today a Fisher X-100 valve amplifier landed in my driveway. USPS had a good day and the package did not get damaged:

The unit was packed fairly well using a lot of tightly wrapped bubble wrap and came with the original manual and a reproduction of the service manual. The sheet on the top right is a map for inserting the valves as was promised by the seller.

We agreed that the valves needed to be removed and carefully packaged individually:

Each tube was wrapped individually and numbered. Very nice job!

And finally the X-100 sat on my bench. The front panel is a bit worn, but on the positive side there are all the buttons and the green 'jewel light' is still there.

This is how it looked out of the box, 'de-valved':

I then unwrapped the valves. And the pleasing surprise was that they may well be the original set! Awesome! Made in USA and Western Germany. This is a ECC83 preamp valve:

This is a GE made EL84 power valve:

And the awesome looking GZ34 rectifier of the power supply. Amazing! A message from a semiconductor free world!

After unwrapping and marveling I plugged them in. All sockets seem to be in nice shape and all tubes  went in easily but with enough friction to give them a nice sturdy support:

Luckily, I read the manual first where it says: Connect speakers or load resistors first then turn it on. Otherwise the unit can get damaged. After connecting my bench test speakers I fired it up. And the jewel came to life! Very nice!

And then after a short while the power tubes and the rectifier started to emit that lovely glow: 

I connected my iPad to the tuner input and cranked up the volume. It sounded absolutely awesome. Johnny Guitar Watson: "Superman Lover" funked warmly out of my speakers with an amazing clearness and full sound. It seems this baby works as was advertised by the seller! Wonderful! A great starting point for bringing it on a sound footing!

Beomaster 8000: Test of Repaired Front Panel Ribbon Cables

After reattaching the severed ribbon cable of the Beomaster 8000 front panel and cleaning the contact pads of the program and source keys, I tested the panel in one of my own Beomasters. It worked nicely, all buttons responding precisely and the rotary encoders doing their job. Here a couple of impressions:

Time to send this panel back that it can continue serving in its own Beomaster!

Beomaster 8000: Repair of a Broken Off Keypad Ribbon Cable

I am assisting a Beomaster 8000 restoration. Today I received the front panel of this unit with an almost completely severed keypad ribbon cable. These ribbon cables easily break off if the Beomaster is opened a few times. Often the glue that fixes the cables to the keypad PCB fails at this age and the 24 gauge leads take the brunt of the cable flex every time the panel is lifted. They only survive this a few times and then they break off. If only one or two break off, this can be fixed by inserting a bit of copper braid and with some flux and solder the connection can usually be restored. However, in this case most of the leads were broken off:

So it was time for some microsurgery. I removed the PCB. This required to cut the original retaining clips, which are of the non-removable type. They can easily be replaced with 3mm retaining clips, so this is not an issue. There is an earlier blog entry that details this procedure.

Once the board was removed, I cleaned up the solder points and then prepared the cable. I had to extend the length a bit since I needed some 'meat' to rebuild the connections. If the cable is too short it is difficult to put the panel into service position with connected ribbon cables. I made eight extensions from an old computer ribbon cable:

Then I soldered them to the prepped ribbon cable leads:

A bit of shrink tubing of the proper color finished the job:

Then it was time to solder the ribbon cable back in:

I also embellished the leads of the other ribbon cable with some solder to stabilize them. They were still intact, but I could see that they also had started breaking off.

Since I was in there, I decided to also clean the contacts of the keypad switches. They usually are a bit oxidized. The oxide layer can easily be removed with a fiberglass pen. This shows the P7 switch before cleaning:

And after:

I did the same with the contact springs. this pic shows one before. The dark spot is the oxide.

Unfortunately, I forgot to take a picture of the cleaned spring pad. They also get nice and shiny after the fiberglass pen treatment.

Then I put the PCB back in using 3mm retaining clips and #4 nylon washers to protect the PCB:

Then it was time to glue both of the ribbon cables to the PCB to protect the cable leads from further bending events. I used hot glue (like the original setup):

That should do it! 

Beogram 4000: Replacement of Incandescent Light Bulbs in Control Panel with LEDs

The Beogram 4000 that I am restoring right now had three broken incandescent light bulbs in the control panel. There are four bulbs, two for the position indicator and one each to illuminate the RPM trimmers. When I initially turned this deck on, no light came from any of the bulbs. Nonetheless, one of the position indicator bulbs was still o.k., but since the two bulbs that illuminate this indicator are in series, this did not help. At any rate, this is a perfect demonstration how fragile these bulbs are at this age, and that a replacement of them with LEDs is a great way to enhance longevity and reliability, and to make sure the unit survives shipping.

I recently developed dedicated SMD LED based replacement units that drop in for the position indicator bulbs. I assembled two and replaced the bulbs with them. I also replaced the RPM trimmer bulbs with high intensity red through hole LEDs fitted with appropriate 3.3k current limiting resistors. This brought them down to the proper intensity, making for a gentle but clearly visible low power illumination of the trimmer slots. 

Here are some pictures of the process. This picture shows the original light bulbs in place:

This picture shows the SMD LED PCBs that I used to replace the two position indictor bulbs:

and here after installing them and putting in the two red LEDs to replace the trimmer illumination bulbs:

After I was done with this I tested the functions of the keypad, and I had to realize that the deck does not switch to 45 RPM. Pressing the key did turn on the 45 RPM trimmer illumination, but the motor stayed at 33 RPM. This meant that the control system worked fine, but that there was an issue at the executive end of things. I traced the signal and found out that the relay that is responsible for changing the resonance frequency of the drive oscillator seems to have given up its ghost. It will be interesting to find a replacement.