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Justin's BG4000

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Craig
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Craig posted on Tue, Apr 6 2021 12:50 PM

Taking Sonavors advice Justin (Bulldog) asked if I would take a look at this.......I cant resist a challenge and I'm not doing much just now so have agreed to take it on..... when I say "me" I mean the forum of course ;¬)

 


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Craig
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As with the control panel I have removed the saddles and cleaned the brass strips in-situ, with the exception of the one NC contact that has to be unsoldered...one down four to go

 


Craig
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Re installed the slide switch assembly and set up the switch (B) that controls the 17cm drop position as it was missing slightly when dropping......all good now. Moved onto the main PCB and replaced the 33 and 45 rpm trim pots with bourne 25 turn pots for better adjustment....always a bit fiddly these, added some heat shrink sleeve too.

 


Beosince98
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Craig:

Re installed the slide switch assembly and set up the switch (B) that controls the 17cm drop position as it was missing slightly when dropping......all good now. Moved onto the main PCB and replaced the 33 and 45 rpm trim pots with bourne 25 turn pots for better adjustment....always a bit fiddly these, added some heat shrink sleeve too.

Interesting seeing these types of trim pots used rather than the standard 15mm ones. I felt the single turn ones gave me decent adjustment as the keyboard pots allowed for the fine tuning. Do you use these only for the RPM trimmers or for all of the ones on the pcb?
Craig
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Craig replied on Wed, Apr 21 2021 7:28 AM

No I only use the 25 turn pots on the RPM trimmers, it's something I picked up from Rudi (beolover)...stands to reason that a 25 turn pot will be more sensitive than a single turn pot, I do however use them for the quiet current trimmers in Beomaster amplifiers...I seem to remember Rudi stating that they are less likely to go open circuit due to the mechanical design than the single turn components......i dont know how this works but it always sounded like a good idea to me......

Craig

Craig
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Replaced the suspect ROE capacitors.....tantals next while I wait for the piher pots to be delivered, seems to be a bit of a shortage of some values recently.

 


chartz
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chartz replied on Sat, Apr 24 2021 11:04 AM

Good job!

However, I for one hate those multi-turn pots.

I never know where the central position is. Plus you have to adapt them to the PCB's which is plain ugly.

I always go for quality potted cermet Pihers for example (the white ones) which are very stable. And at least I know the cursor's position!

Raplacing electrolytics and tantalums (tantala? Stick out tongue) is a must do, but honestly on Beograms they keep their value and ESR, I find. I always measure the old caps out of curiosity and they are usually perfectly okay. 

In amps, however, that's another story... 

Jacques

sonavor
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Yes, good work as usual.  I like the multi-turn trimmers for no-load current adjustments on amplifiers and for the Beogram speed adjustments. The fine dialing in of the value is really nice. I use single turn trimmers for adjustments that should only need to be set once. 

-sonavor

Craig
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New single turn trimmers delivered and installed.......I haven't seen white piher trimmers for sale anywhere in the UK?

 

 


chartz
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chartz replied on Tue, Apr 27 2021 7:24 PM

Craig:

New single turn trimmers delivered and installed.......I haven't seen white piher trimmers for sale anywhere in the UK?

I don’t know. I buy them here in France. Digikey have them.

 

Jacques

Craig
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I just love this gadget I acquired from Rudi.....bit of an extravagance I know, but I do like it Yes

 


Craig
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And the 45rpm

 


Craig
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All done and ready for shipping back.......I just hope it survives the one day in transit Surprise

 


chartz
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chartz replied on Wed, Apr 28 2021 4:56 PM

Nice!

By all means, pack the platter separately.

Jacques

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