[hcraig244]

Alf

Does the record detection circuit work with the replacement bulb….or are there still issues?

Craig

[hcraig244]

Bernie

this pic shows the failed transformer wiring and measurements from my problematic transformer……the only problem with it turned out to be the low measurement on the 230v secondary output to the neon lamp, the rest of the measurements where the same as those on a fully working machine…..as can be seen the 0.89k should have been 1.3k

[hcraig244]

Have you checked the transformer out fully?….measured the primary and secondary windings to be sure there’s an issue? tried disconnecting the secondary outputs and powering up?…..I did a lot of checks before I finally condemned the transformer due to them being impossible (mostly) to source….and bespoke toroidal transformers being so expensive to commission.

[hcraig244]

this is the final wiring with the load resistor (not shown) wired to the input of the regulator before the small capacitor 

[hcraig244]

Another thing that will help is if you look in the archive forum 2012-2022 you should be able to find the first part of this thread…….may make things clear for you

[hcraig244]

Bernie

Sorry for the late reply…..been a bit busy with work etc. The GL90 neon was connected directly to the incomming 230vac supply down stream of the fuses…..the supply needs to be connected through the reed relay contacts just as it is now (so the lamp only comes on when start is pressed) I think all the parts I used are documented in this post….but if you need any more info let me know

Regards Craig

[hcraig244]

I would also replace ZF18 Zener diode….check the other transistors around the voltage regulator too…..something caused may have caused the SE8002 to short out.

Craig

[hcraig244]

Ok……one thing at a time.

1. For some strange reason the internal wiring which connects the AUX signal DIN to the amp is wired differently to the TAPE input DIN, I found this out the hard way. Connect your signal to the phono plugs instead of the DIN connector for the AUX input and see if you then get sound to your speakers.
2. The Hi and Lo s are latching switches that need to be pushed forwards to engage or disengage….these are used if your input needs to go through the pre amp stage or not…a low signal will need to (I think this is right…..). The + and – trim pots can be set by ear….they adjust the volume of each speaker to balance the sound.
3. I will need more info for this question….and maybe some pics?

[hcraig244]

This is a pic showing the lamp still on the push fit tab

[hcraig244]

You need to take the top off, remove the screws holding the amp PC down….it’s on a hinge so will lift up and can be put into the service position which is vertical. This allows access to the power on bulb, its a push fit onto a tab and can ce carefully pulled backwards untill released, you can then unscrew the lamp and replace it…..make sure you use the propper voltage…I think its 60vdc

[hcraig244]

All complete and fully tested…..does sound very good for an old girl, I think it can now be identified as restored……

[hcraig244]

Made a start on the front panel and curser…..takes quite a bit of fiddling around to get the felt pads back in along with the nylon studs on which the curser rides…..

[hcraig244]

Hooked up to a Beolab 5000 and an antenna, and I have to say that in spite of the occasional unexpected minor issue this tuner sounds tremendous….crystal clear and very stable….all that remains is to put it all back together ;¬)

[hcraig244]

Completed all the component replacements….including the “fairchild black blobs”, fitted BC550B’s.

[hcraig244]

Deciding the way forward was to replace the cloudy lens with the not so cloudy lens on the one I had just installed I set about dismantling the not so cloudy meter and discovered the internal connection from the + post was loose….tightened it up put it back together and having removed the newly extended + wire I soldered it back in place…..and yes everything worked fine!……spent a couple of hours on this

[hcraig244]

However I extended the + wire and soldered the cloudy meter in place and ran another test, all worked fine

[hcraig244]

The polarity of the meters are opposite, someone has erased the + / – markings from the left hand side meter and marked them up opposite to what they where…….the right hand side meter is the one with the milky lens and still has the + / – markings unchanged,

The negative marking can be seen against the right side post, the meters have different shapes too….change in design down the years I expect.

[hcraig244]

Thinking I may have damaged it during cleaning I took it out, looked ok and when I put my multimeter across it to check the moving coil continuity the needle deflected 3/4 up scale, as you would expect from the current from the meter set to ohms. I got out a meter I recently replaced due to severe clouding of the lens to compare….and found this curious thing……

[hcraig244]

Started by checking the 240v supply to the transformer…..all good, 32v output to the new rectifier and around 40vdc out of the rectifier. Checked the 20vdc supply and found it was around 29vdc…adjusted the new trimmer I installed and brought it back to 20vdc……checked the voltage to the power ON lamp and that was good too…..so replaced the lamp and of course it illuminated ;¬)

Connected a antenna and adjusted the tuning dial, the stereo lamp flickered as it passed through live broadcasts which was very encouraging…..however the tuning meter stayed hard down throughout.

[hcraig244]

This is true Soren….I received this from Frede some time ago:

Craigh,

 

It is actually a ”short list” ?

BC 550B for npn

BC560B for pnp

 

When the Beolab was designed (before 1967) only a few transistors were available is really low noise versions – therefore B&O have chosen a number of different types of coarse also being able to be used and meeting the actual voltage level. But I have for many years used the above type in the pre-amplifiers.

And I am using the transistors type B because higher gain in classic electronics design is not a good idea (this is my opinion ?)

B U T — for the power amplifier and the power supply – I only use the original RCA types !!!

For the output power transistors and psu transistors — I am only using the original Motorola or RCA (there are to many “fake” 2N3055 out there).

When I am writing the original it is actually the original because I re-use these transistors from Beolab 5000 which is scrapped.

 

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