ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
A peak into the side of the control panel reveals there are some ICs on that board. Doesn't appear to have any electrolytic capacitors that need replacing.
Tomorrow I'll check my inventory of capacitors and trim pots to see if I will need to order any parts.
Looks good John!
I renewed every single cap in my example, and it made no difference. It worked fine before and equally fine after. I checked the old caps which were all within tolerances. Pretty amazing!
Jacques
Thanks Jacques.The first thing I am going to focus on is getting the turntable power in order. I'm a little concerned with that because the old 0C1 and 0C2 (2000uF) capacitors appear to test out okay. The previous owner said they couldn't get the unit to work and they replaced those caps...but it makes me wonder if those caps were really a problem. I'm thinking there will be something else. So first I need to get correct power on the deck. What about those two splices in my picture here? They are two red wires that come off the transformer. One wire heads to the 8009011 board 2MS1 relay. The other looks like it goes to the strobe lamp. Where I show the tweezers holding the wire that goes to the strobe lamp - is that where 0R1 (27Kohm resistor) is?
Not sure. If memory serves, the resistor is in the yellow sleeve. The spliced wires should pass underneath the transformer.
The black splice with the red and yellow wire is original. Lead colors too.The rest of the splicings are not original and leads me to think that the transformer has been replaced at some point.Of course those splicings should have some heat shrink tubing or similar.
Martin
Yeah, I will reconnect the splices and use heat shrink tubing for sure. Does the transformer look like a B&O transformer? I should be able to work on it later today and get a US power cord attached. Once I can plug it in I can see what the voltages coming out of the power supply look like. If the voltages are all there, I can continue with restoring the rest of the turntable. If the voltages are missing or off, I'll have to figure out the next step from there. I hope the transformer is good or else that will put a quick end to this project (until a replacement can be found).
The transformer looks very much '70s B&O to me,but if you have any doubts about it's originality, I'd disconnect all secondaries and measure the voltages before reconnecting the rest of the electronics. Whoever replaced it might not have given that much thought about how it will operate when switched to 110/130 V mains.
--mika
It looks the same as mine John.
Tonight I got a new power cord installed. The old one would not work in the outlets here in the US.Here is the original power cord.
To replace the power cord I had to disassemble the voltage selector and fuse box. The original fuse box on this Beogram had damage to it and someone attempted a repair using epoxy. I decided to switch out that fuse box with a nice one out of another Beogram 4002, type 5503 (that will be a future restoration project).
This is the voltage switch box (part of the fuse box assembly) with the new power cord soldered in.
Here is the complete power cord replacement. I had to look around several places to find a nice, gray power cord. Tomorrow my power supply capacitors will arrive and I will fix the two spliced wires with heat shrink tubing. I changed out the yellow sleeve over a fuse that is on the 8009011 board with a clear plastic sleeve. I will put a clear plastic heat shrink tube over the 27K ohm resistor as well.
I should have all of the parts I need to continue now.On the platter motor capacitors though, the Beogram 4000 originally has a 4000uF, 25VDC polarized capacitor and a 150uF bi-polar capacitor. The best I can do is get a 4700uF and a 220uF as replacements. Those are the replacements I used on my Beogram 4002, type 5503 so I am going to use those values again here. For some reason, 4700uF is a common and easily obtainable (low cost - $2 USD) capacitor. If I had to get a 4000uF, they start at around $14 USD.
When you'll succeed in repairing your deck (and I'm sure you will) you'll might have to change both fuses in the fusebox, given the 40W power consumption (twice the power consumption of the 4002-4 !!!!!) and the 117 VAC. In mine, I've put two 0,4 AT fuses. (based on the 0,34A current)
As I recall, this fact is not mentioned anywhere in the service manual: this might be because this model was never meant to cross the ocean. I would be curious to know how many of these exists in Americas.
By the way, I was wondering if the original 27K resistor, leading to the strobe, was actually were you thought it would be: I always thought it was under the silver tape in the middle of the deck.
Guillaume
Thanks for the information Guillaume. That is good to know. On the previous picture above, you can see the exposed 27K ohm resistor. I removed the black tubing that was around it. When I fix the splices I am going to put a clear heat shrink tube around the resistor. I'll show a closer picture once I do that.
Tonight I finished the heat sink on the splices and the 27K ohm resistor (0R2). Next I changed out 0C1 and 0C2.
After that I decided to see if power would come on. It didn't so I dug in and checked the 0C3 and 0C4 (3000uF) caps, The 24V zener, 0TR1 and 0D1. Those components all tested okay but no power will come on. I opened the fuse box and one of the 0.25A fuses had blown. I will try to draw out the wire paths as measured on the unit versus what is in the schematic. Measuring the primary windings, there is one pair of wires (one red, one white) that measure 47 ohms between the two. Then there is a cable with three wires (yellow, green and black). Green to black measures 39 ohms. Green to yellow and yellow to black both measure open circuit. I need to figure out if that means the transformer is shot.The fuse that blows is the one from the red primary wire, not the yellow wire. I'll have to draw out the wiring diagram to show what I see on the Beogram versus what the service manual shows. Here are the two cables going to the primaries.
I think 250mA is for 240V AC. I wonder whether you won't have to adapt those fuses to the unit now being American? It is an alien after all.. It doesn't yet speak the language. Like double their values, if I get my Ohm's law right?
Try 500mA fuses!
Here is a trace of the power input selection switch and the transformer primaries. What I trace doesn't appear to match the service manual schematic. The diagram shows the resistance I measure across the primaries. It also shows the fuse that blows with a red X.
Here is the inside of the voltage selection switch again to show the wire colors per my diagram.
Redrawing my diagram, my measured values do match up with the schematic. So I am thinking I must have a bad transformer after all.
The transformer in this deck looks original.Two types were used, the other one has a metal housing partly covering it, if I remember correctly.They are fully interchangable but unfortunately both types are equally prone to shortening their primary windings.
Dillen: The transformer in this deck looks original.Two types were used, the other one has a metal housing partly covering it, if I remember correctly.They are fully interchangable but unfortunately both types are equally prone to shortening their primary windings. Martin
Or opens ? It appears that I have an open winding. Are there any options to get these transformers repaired or a suitable replacement?
I pulled out the Beogram 4000 transformer so I could measure the primary and secondary connections with nothing attached. I got the same result, the yellow primary wire measures open to both the green and the black primary leads. The transformer base is set into some epoxy so it would probably be difficult for someone to repair. I will have to either find a replacement of spare or a re-manufactured transformer. I don't know the exact specifications of the transformer to request a re-manufactured one though. That information isn't in the service manual. I suppose the worst case scenario for restoring one of these turntables would be to redesign and build a new power supply. That would be better than not being able to use the turntable but I am still quite a way off from that drastic option.
How about wiring the good primaries differently and see what voltages you get?
It should be possible to do without the bad one altogether, for 120V or 220V - I bet the 44 ohms winding is a 120V one, the bad one being a 20V tap for UK back then.
And keeping those 0.5 fuses in mind of course.
Are you suggesting to try connecting power to the removed transformer like this and measure what is on the secondaries?
Yes, this should work John. What you have is just a bad 110V coil. That said, the green to black resistance is surprisingly high.
In almost any European transformer there were two 110V primary windings connected in series, and for export they added a few more coil turns for the extra 20V (so, green-black here) in the UK. Until recently, we had a 220V power grid and now that the whole Europe has 235V that extra tap is a blessing!
Test with a Variac, and monitor what you have at the secondaries.
Thanks for this information Jacques.
EDITEDI connected and made the measurements on the transformer. Using my variac I took the voltage up to 125 VAC and measured the three pairs of secondaries. The first one (two red wires) goes to the speed indicator strobe. The voltage there was 1:1 so I get 125 VAC at the secondary.UPDATE: The secondary is not 1:1. The output should have been around 200 to 220 VAC (not 125 VAC). The second one (two yellow wires) goes to the diode bridge rectifier circuit on the chassis. The voltage there was 17.7 VAC. The third pair (two blue wires) go to the diode bridge rectifier circuit on the 8009011 board. That voltage is 5.4 VAC.Here is a diagram of the test and measurements.
I set up a simulation using the transformer values I measured. It looks like I should be able to use the transformer connected as Jacques described and get the voltages the Beogram needs.
Well done, you now have a 100% American BG4000 transformer!
I hope so and I really appreciate the help Jacques. Now I can proceed and get the power back installed in the Beogram.Thanks!
And we do appreciate your really helpful diagrams. I wish I could do the same as quickly as you produce them!
I got the transformer re-installed and power wires re-routed. The power capacitors are also in place now.For the AC power, I took out the selection switch as it serves no purpose anymore with this transformer. This one will be fixed for 130 VAC.I connected each of the two AC power cord wires to one of the two fuses in the fuse box.
The red and black transformer primary wires went to the other ends of the fuses. The green and white wires were joined together while the yellow primary wire is not used.
Here is the re-installed transformer and fuses.
Finally, the new power and motor caps re-installed.
Now I am back to the beginning of the Beogram 4000 restoration project. I can plug the Beogram in and get voltages on the power caps. The two 3300uF caps charge up to a little over 22 VDC. The two 2200uF caps charge up to a little over 5 VDC on one and a little over 6 VDC on the other.The fuses (0.5A installed now) don't blow either. Unfortunately, though, the Beogram doesn't not operate. I get no activity when I press the ON button. I suspect maybe the reed relays aren't functioning so I'll have to trouble-shoot that next.
I the service manual trouble-shooting flow diagram for no power. It points me to 1R19 on the main board where I do not get 24V. That refers to a possible problem with relay 7600013. I don't find that in the schematics but it looks like the relays on the power board should be engaged and they are not.
One more check before I turn in.I measured the node between 2R14, 2R15 and 2R16 that is marked 11.5V on the schematic (highlighted in yellow on the picture). When I apply AC power to the Beogram, that voltage starts out at 0.9 VDC. When I press the ON button, that voltage does go to 11.5 VDC. So I am able to see that the ON button is attempting to function.