Beomaster 2000 Type 2801: Replacing Some Components and First Music Listening Test

I received most of the electronic components I needed to restore this Beomaster 2000 receiver.
Compared to the last few Beomaster receivers I have restored this one will have the least amount of capacitors replaced.  As I mentioned in the previous blog post ...for this unit I will leave in all of the red tantalum capacitors if a spot check shows them to be good...and it did.

Here is a small sampling of three different tantalum capacitors from the Beomaster 2000.

I didn't remove and test every single tantalum but I tested enough where I was satisfied the plan to leave them in is sound (sorry for the unintended pun :-) ).

I did replace the electrolytic capacitors, the no-load current adjustment trimmers (two...one for the left channel and one for the right channel) and the 2D8 bridge rectifier.

Here is a before and after photo of the 470uF 2C24 capacitor and the 2D8 bridge rectifier (located on PCB 2).

Before:

After:

The output amplifier board (PCB 7) had seven electrolytic capacitors to replace and two 250Ω trimmer resistors for the left and right channel no-load current adjustment.

Before:

After:

Note: The thermal compound on the transistors mounted on the rear heat sink of the Beomaster 2000 cabinet was still soft so I left those alone.  If there ends up being a problem with the transistors and I have to replace any, I will rework all of the output transistors.
For now...they are left as they are.

PCB 5 (IF & Preamplifier) only has two electrolytic capacitors to replace.  Here are the before and after photos for that board.

Before:

After:

That sums up the PCB component replacement tasks.

PCB 3 (Pre-set Tuning board) required desoldering of the five pre-set dials.
The issue with this board was that the black, plastic adjustment knob for each preset was slipping.

I cleaned all of the preset components with some fader lube, glued on the plastic knobs and then reinstalled the five presets to PCB 3.

Next, it was time to check powering up the Beomaster and checking voltages.

I set the voltage selection switch to 130 VAC as here in the USA the line voltage is closer to 130 V than it is to 110 V (the other voltage switch selection option available to me).

On these initial power up tests I use my variac and dim bulb tester to protect any short circuits to ground in the Beomaster power supply path.

As you can see the line voltage is closer to 130 V than 110 V so 130 V is the best selection for my area.

For reference here is the Beomaster 2000 Type 2801 line voltage supply wire routing for the four voltage select options.  Top left is the wiring for my selection.

With the Beomaster turned on (Tape selected) I measured the secondaries off the transformer.
One set should be at 26 V and the other should be 46 V.

Those are good values for the power coming in.

Checking the resulting ±30 VDC rail voltages I measure -

Those measure good.

Now to check the +26 VDC adjustment called for in the Beomaster 2000 service manual.
I monitored the +26V test point and adjusted the trimmer to get as close to 26V as I could.

After that I adjusted the output amplifier no-load current for both channels per the service manual.
The adjustment calls for no speakers connected, the volume level at zero, the amplifier warmed up and a measurement of 10mVDC across emitter resistors (7R119 : LCh, 7R219 : RCh).

Here are those measurements using the new Bourns multi-turn trimmers I installed to adjust the voltages.

Left Channel

Right Channel

Those are all the initial voltage checks I wanted to do.
Now to hook up speakers and see if I have music playing from this receiver.

This picture shows my little iPod Nano providing the music source to the Beomaster 2000 Tape 2 input.
You can also see in the photo that the lamp for the tuner dial is illuminated.

Listening to music from the restored amplifier is a nice milestone to reach in the project.

Normally I would move into some performance testing but there are a few problems to address with this Beomaster first.

There are no lamps lit up on the PCB 4 Indicator circuit.  It has four 12V, 30mA lamps and they appear to be burned out.

I should have checked that earlier but now I will have to wait for those parts to arrive.

When examining the tuner dial cord I discovered another problem.  The cord has a spot that is badly frayed.  I don't want to put in all of this work only to have the cord break later.  I ordered a replacement for that and will also have to wait for that to be delivered.

I also had to repair two of the tuning cord pulley posts because there were defects in the plastic parts.

On the left side of the dial window the plastic mounting tab for the pulley was broken when I initially checked over the Beomaster 2000 inside.

I was able to glue that broken piece back together but the break across the plastic part will see a lot of stress so I don't think it will hold up over time on its own.

For that reason I fashioned a u-channel reinforcement part that I could epoxy into place across the break.

The right side of the dial cord assembly also had a problem.
There appeared to be a missing pieces (a plastic tab) that keeps the metal rod for the dial assembly from pulling out of place.

I fashioned a second 3D part to keep metal rod in place. It too was installed using some epoxy.

That was not the end of the problems for the right side dial cord pulley though.

I could easily see that the pulley assembly was loose and would not remain in place when the tension of the dial cord was pressing on it.

It turns out there were some cracks in the plastic mounting post for that pulley assembly.

So the mounting screw would expand the cracked mounting post when pressure from the dial cord is applied.

For that repair I made a ring for the post so the cracks in the post couldn't expand.

That work out really well.  Satisfied that repair would work I epoxied the ring in place.

This Beomaster should be ready for further testing once the replacement lamps and new dial cord arrive.

Beogram 8002 From North Texas: Replacing the electrolytic capacitors

Moving on to the electrical tasks on this Beogram 8002 project...
There are electrolytic capacitors in the Beogram 8002 in four locations: the floating chassis, PCB 1, PCB 2 and inside the transformer box.  Typically not all of them will be out of tolerance but it is a good move to replace all of them rather than wait for them to fail one at a time. 

I will start by showing the replacement of the two capacitors on the floating chassis.
These two, 0C1 and 0C2, are part of the Beogarm 8002 +5 VDC regulating circuit.

The two capacitors are easy to get to although the yellow, black and blue wires should be disconnected and moved out of the way first.

On this project the Beogram 8002's owner had already purchased a capacitor kit for it. The kit contains most of the capacitors I normally replace and they are good quality capacitors so I will use them.

Here are the new new 0C1 and 0C2 capacitors installed.

PCB 1 is the main board of the Beogram 8002 while PCB 2 piggybacks on top and inside a shielded, metal box.  

PCB 2 houses the Beogram 8002 microcomputer IC and has just one electrolytic capacitor to replace.
It is a difficult one to deal with though.  The negative lead side is soldered to both the top and bottom layers of the board. In addition, the space is a very tight fit and is right next to the microcomputer IC.

This lone electrolytic capacitor, 2C28, is for the +5 VDC supply voltage to the microcomputer IC...so pretty important :-).

  
























I like to cut the exposed leads on the 2C28 capacitor to remove it first, then desolder and remove the remaining parts of the lead once I have more room.

This photo shows the other side of PCB 2 and the other two solder points of 2C28.

A number of years ago we started replacing the 40-pin IC socket for the microcomputer device on these Beogram 8000/8002 restorations.  Removing the old IC socket provides more operating room and the new 40-pin socket with tulip style contacts is a sturdier part than the original socket. It provides some extra insurance in reliability and is easy to replace during this capacitor replacement task.

The new 2C28 capacitor is in place and so is the new 40-pin IC socket.

I re-inserted the microcomputer IC (while taking electrostatic precautions of course).
I will apply new thermal paste to the top of the microcomputer IC later when I re-install the metal lid that has the heatsink for it.

One other step I performed on PCB 2 was to use a soldering tool to reflow the solder joints on all of the board connectors.  We have found that those connector-board solder connections can become faulty over time and they are not something a visual inspection can always catch. It is safer to just reflow the solder.

In case any Beogram 8000 owners are wondering, the microcomputer IC in the Beogram 8002 and Beogram 8000 are not compatible. The PCB 2 board and housing look the same but the functionality of the microcomputer IC itself is different enough where they are not interchangeable.

Next is PCB 1
I used this photo above but I will include it again.  The photo shows all of the PCB 1 electrolytic capacitors that will get replaced except for the one hidden underneath the metal shield box.  I will show that replacement capacitor a little later on.

As I said earlier, not every electrolytic capacitor in the Beogram 8002 will be out of tolerance but there are always some that are...

Both of those capacitors are part of the Beogram 8002 power supply circuitry.

The largest capacitor, 1C27, which is for +15 VDC supply filtering was still in tolerance but it is being replaced now while all the other work is being performed.

1C27 is a little unusual in that it has a three prong base for its negative lead.  The three prongs are for mechanical support and I have never found a modern replacement for this type of packaging.
The new capacitor is the common, two-lead, through-hole style of capacitor.

The Beogram 8002 PCB 1 board expects the 1C27 capacitor base to connect two of the board ground connections via that three prong base.  That can be accomplished with a jumper wire on the trace side of the PCB 1 or I can pop off the three prong base from the original 1C27 capacitor and re-use it.
I like to opt for the second option.

The new 1C27 capacitor positive lead goes right in the center of the three-prong mounting ring.
The negative lead gets bent around the mounting ring and soldered to it.

That is it. 
The new 1C27 capacitor will fit into the original PCB 1 holes and soldered in place the way the original was.

Here is that PCB 1, C28 capacitor that is underneath the PCB 2 shield box.

On PCB 1 on the other side of the shield box is 1C4.

That accounts for all of the PCB 1 electrolytic capacitors.

Just as I did on PCB 2, all of the PCB 1 board connector solder joints were re-flowed with solder.

The last electrolytic capacitor, 4C1, is a non-polarized capacitor located inside the transformer box.
The modern replacement capacitor is much smaller in its physical size so we created a 3D printed mount for it.

While I have the soldering tools out I took the opportunity to replace the audio muting relay on the Beogram 8002 output board, the small board that the 7-pin DIN connector is mounted to.

This is another precautionary change.  We have seen enough of these relays start to fail where it is safer just to replace them rather than wait for them to fail.

Here are the before photos.

I am including a picture of the trace side as it shows all of the wire connections for the phono audio signals.  The connections look really good on this Beogram 8002 output board. The last two Beogram 8002 output boards I worked on required re-soldering of those wires because they were poorly soldered and the connections were failing.  I expect the output board to always look like this one.

Here is the new Omron relay installed.

In the next post I will lubricate and re-install the tonearm assembly.