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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I should also mention that the base of 2TR5 also turns on (from 0.2V to 0.7V) when the ON button is pressed. So the relays are being activated...they just don't respond.
sonavor: I should also mention that the base of 2TR5 also turns on (from 0.2V to 0.7V) when the ON button is pressed. So the relays are being activated...they just don't respond.
That proves that the base of that transistor is high, nothing yet on the relays. What do you have on the collector or over the relay coils?
--mika
Sshhhh... John is asleep, don't wake him up!
Jacques
I'm awake now :)
Yes, I didn't think about checking out the collector of 2TR5. Measuring that node reveals that it is starting out at 0.26 VDC, then switches to 0 VDC when the transistor is engaged (when the ON button is pressed). That is the same node as the 2D3 (1N4148) anode. The cathode side of 2D3 is about 22 VDC. The node where the two relays and 2R18 (390 ohms) meet always measures 0.07 VDC.
Good morning John I think I would disconnect the relay coils from everything and measure their dc resistance, and do the usual diode tests for that transistor.
Good morning Mika. Well, it is turning out to be not so good of a morning. The 2TR5 transistor measures fine but I am unable to measure the relay coils because each one has a broken wire. So that is why the relays wouldn't engage. Those control wires are the small magnet wire type so impossible to reconnect with the relays in place. It will even be a tough job with the relays removed as the remaining lead is too short to reach the post. Is it possible to replace these relays with a modern equivalent?
I'm sure it is but they should be fixable if you take the yellow tape off and pull one turn of the tiny wire to get to the post.
It'll work!
That is my first choice...to attempt the repair. Here are the two relays. Each has a break with a very short lead.
I have the first one re-soldered and I am working on the second one.
Here's the second one. Now I have to get everything wired back up correctly.
I didn't expect anything else than a repair
Of course it would be possible to replace the relays with something modern, but they seen really compact (reed contacts inside?) so it might be a problem fitting them physically.
I'm not out of the woods with the relay repair yet.On the first relay, I measure a little over 400 ohms across the coils.On the second relay, the solder repair on the short lead (inside lead) took but that short lead was broken further in and just pulled out when I tried to measure the coil. I don't want to unwind the relay to get to the other end but I don't know another way to find it.
My attempt at repairing the relay failed. While I was able to rewind the coil wiring, the glass tubes with the reeds broke so that kills that option. The other relay looks like it might work but I can see a chip in one of its reed tubes as well so I don't think I would trust it long term. I think I'll have to look for a new type relay to install.
I do see there are people selling the glass tube reed replacements. But what current and wattage ratings are correct for this unit?
sonavor: I do see there are people selling the glass tube reed replacements. But what current and wattage ratings are correct for this unit?
I don't know. The ones I have in stock are the only ones I've ever come across and they always seem to fit.
I ordered some glass reed replacements that are 37mm long and 5mm diameter. They are rated to 230VAC and can handle 1A plus 21W. It will take at least ten days for them to arrive though. The original tubes are around 34mm so I think these should work.If I were to opt for a modern replacement, I wonder if these DIP type reed relays would work?They are 24V and rated at 1A, 15W and 200VAC switching voltage. The datasheet is here.
sonavor:If I were to opt for a modern replacement, I wonder if these DIP type reed relays would work?They are 24V and rated at 1A, 15W and 200VAC switching voltage. The datasheet is here.
As the two relay coils are in series, I believe you will want 12V types (disclaimer: I haven't really looked into the schematic beyond the snippet you posted on the previous page).
But I'm sure your replacement will work fine, as mine do.
tournedos: sonavor:If I were to opt for a modern replacement, I wonder if these DIP type reed relays would work?They are 24V and rated at 1A, 15W and 200VAC switching voltage. The datasheet is here. As the two relay coils are in series, I believe you will want 12V types (disclaimer: I haven't really looked into the schematic beyond the snippet you posted on the previous page).
The 12V versions are rated at a 0.5A maximum switching current and maximum switching load of 10W.
While I wait on my glass reed relay replacements I am going to get the power supply board reassembled and ready. I wasn't happy with my relay coil repairs. In fact, one of the short lead repairs broke. So I ended up rewinding both relay coils to make sure I had good leads coming off them. One of the relays I ended up doing twice. After rewinding it the first time, the starting point lead broke on me. What a pain. On the second go-round I decided to mount a couple of small metal posts to the relay coil frame to attach each coil lead to.Here is my high tech relay coil unwinding machine. It is very tedious to do this and I need a way to unwind it quickly while, at the same time, being careful not to break the wire. The wire is hair thin and very delicate.
Here is the second rewinding of the coil I had problems with. I soldered the starting wire lead to the tiny metal post. This is about a quarter of the way into the rewind.
Once I got the coil rewound and taped, I attached the other end of the coil wire to another post I mounted on the other side. Testing the coil resistance with my DVM I got 392 ohms.
I have two of the original glass reed relays intact so I tested the relay operation. I connected a variable DC power supply to my relay posts and measured continuity of the glass reed relays with my DVM. One of the relay reeds measures open and 0.6 ohms. It switched on at around +10 VDC.The other relay reed switches at about +7 VDC but measures open and 6 ohms. So I'll wait until I get the new set of reeds before reinstalling this relay.
Excellent work so far John. Looking forward to the next episode!
This weekend I got the second relay coil rewired and the coil leads attached to some terminal posts connected to the relay frame. Here is the power board with all of the components removed.
Here is the power board with the re-wound relays mounted and everything reconnected. The only thing missing are three glass reed relay replacements. They should slide right in from the bottom and attach to the slotted posts I have installed. I re-attached the yellow, red, orange and grey wires at the bottom of the picture to the underside of the board so they will be well out of the way when I insert the glass reed relay components. Hopefully they will arrive next week.
It looks like I finally have ignition on the Beogram 4000. A local guy advertised a NOS package of glass reed relays sold by Archer (RadioShack) many years ago. I went ahead and picked them up for a couple of dollars. The relays I ordered last week are coming from Europe so may be another week.I mounted the new reed relays and applied power. The Beogram motors are spinning and I have a few lights. I don't see the strobe flashing so it is probably out.
I was hoping my reed relays would fit nicely into the slots of the little posts I installed for them but leads are too big in diameter. They could still be soldered to the posts so I did that. It doesn't look as nice as I wanted but the relays are functioning.
The next step is to start checking the functions on the other boards. The drive screw for the tonearm current has the pulley removed. It came that way but the set screw is there so I will have to re-attach it to the drive screw and install the belt.
I moved into the tangential drive section of the Beogram 4000 this weekend. Now that power is restored to the turntable I needed to see what the turntable does when it is turned on and buttons pressed.The first step was to re-attach the tangential drive shaft pulley. There is just a small set screw. Once re-attached, I noticed the pulley rotates with some wobble. Never-the-less I gave the Beogram a whirl. The tonearm assembly moved forwards in search of a record, reached the end and came back to the start position and stopped. So far so good. I don't have the platter installed at this point so I have to just observe the platter motor pulley turning. It turns and increases speed when 45 is pressed. Later I will measure the sine wave driving the motor with my oscilloscope.
The tonearm appears to function properly so far. I will still have to do some further tests of course (per the service manual) but it is a good sign that it moves. I don't like the wobble of the pulley though so in checking it out I found a couple of cracks in the pulley mount (where the set screw tightens).
I repaired the cracks with some Araldite epoxy and let it dry. That was a slight improvement but it looks like there is too much play when the pulley is attached so I inserted a small, nylon washer. That made a big improvement. The pulley still has some wobble but the arm assembly seems to move smoother.
Another thing I did while working on the tangential drive was to pull the drive shaft out and clean it. I also cleaned the socket the drive shaft fits into on the tonearm assembly.
Here it is re-assembled.
I am able to see some of the lights working when the turntable is running. The arm movement detector lamp glows and the tonearm position indicator scale illuminates. I don't see any activity in the strobe lamp assembly though.
I am not sure yet if the tangential drive system is fully functional yet. The forward search speed and the return speed seem much slower than the Beogram 4002 turntables I recently worked on. I haven't learned the specifics on each control button yet so I need to read up on the that next.Regarding the tangential drive shaft and pulley wobble, I considered swapping out the drive shaft and pulley from my spare Beogram 4002 Type 5503 unit (one that is in my repair backlog). The drive shaft is the same length although the 4002 shaft has more threads. When I had the drive shaft out for cleaning I compared the two. You can see all of the dirt that was embedded in the grease of the drive shafts.
The pulley end of the drive shafts are different between the 4000 and 4002. The pulleys are the same diameter and use the same drive belt but drive shafts and pulleys have to mate together as a pair. The 4000 shaft has a flat cut-away a the end for the pulley set screw and the pulley has a matching hole for the drive shaft end. The 4002 has a round end so its pulley does as well. The 4002 drive shaft is mounted into the mounting bracket in a manner that it does not come out. The 4000 shaft pulls out of the mounting bracket when the pulley is detached.
Here is the front side of the 4000 and 4002 (type 5503) mounting bracket.
For now I am going to leave the original Beogram 4000 tangential drive shaft and pulley installed unless I discover the drive shaft (and pulley) are preventing the turntable from operating correctly.
I still have some concern over the Beogram 4000 transformer. Although the turntable appears to be functioning correctly, I had one incident on Saturday where the circuit breaker for my shop disengaged when I applied power to the Beogram. I was using a variac to switch power on (like I have done every time so far), when power went out in the room. I turned the variac off, then clicked the breaker back on. When I re-applied power with the variac, everything worked as normal again. Very strange and suspicious so I am worried about the health of the transformer since I believe it would have been the most likely culprit in throwing the breaker.
My next steps are to check the platter motor voltages for 33 RPM and 45 RPM.
Here are the results of the platter motor checks and the tangential forward and reverse speed checks. All of them are out of adjustment.The platter motor drive signal should be a nice sine wave close to, but not over 6.5 VRMS. The sine wave will be about 42.3 Hz for 33 1/3 RPM and 57.3 Hz for 45 RPM. I measure the frequencies for those speeds pretty close (42.46 Hz for 33 1/3 RPM, 57.40 Hz for 45 RPM). However, the voltage levels for a clean sine wave had to be dropped down to 1.526 VRM (33 1/3 RPM) and 1.436 VRMS (45 RPM). Going above that (using trim pot 1VR3) results in a choppy signal.
For the forward and reverse speeds of the tangential arm drive, the service manual says I should measure between 2.5 and 3.0 VDC at trim pots 1VR5 (FO) and 1VR6 (RE). I measure close to 6 VDC for both directions and the trim pots have no affect on the voltage across the DC motor.Here is a picture of my DVM and scope probe set up for the platter motor and tangential arm motor voltage checks.
Here are the trim pots for adjusting F0, RE (blue arrows) and the platter motor voltage (green arrow)