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Wiring of a radio's power supply

Richard9025

May 24, 2016
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Hi !
In this schematic of a radio , can you explain me what these wires do ?
So , I highlited on the schematic the switch from the volume potentiometer (the volume control also turns off/on the radio , it is a potentiometer with a switch) , there isn't actually 1 switch , but there are 2 switches (highlited in the GREEN rectangle on the schematic) , when the volume is off , there is no continuity between each one of the pins but if it is on , there is continuity like shown in this diagram : (the diagram represent the pin of the 2 individual switches that are both triggered then i rotate the potentiometer's button to the left , it controls the volume and has an off state also)

gloria4 1989 - Copy.jpg
So , what is the red wire ? what is its job ?
If I hook the radio to batteries and the yellow wire (point 40) to pin 2 and 4 , and the + of the batteries to pin 3 and the red wire to pin 1 and i turn it on , nothing happens , the radio starts(works flawlessly) only if i disconnect the red wire , so there shouldnt be a connection between the red wire and the + of the batteries ?
red wire = the wire that is highlited with a red rectangle in the schematic
green rectangle = the 2 switches (see schematic)
full resolution image : https://goo.gl/photos/ZHY153DTRpvYTchU7
also attached down below
Thanks !
 

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davenn

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gloria4-1989-copy-jpg.33182


is that the switch connections ??
 

Richard9025

May 24, 2016
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Yes , the red line= continuity when it's turned on , 1-2 and 3-4 (there's no continuity between 1-3 , 1-4 , 2-3 , 2-4)
 

73's de Edd

Aug 21, 2015
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Sir Richard9025 . . . . .


Initially consider this further info on your drawing

Gloria Switch.png

Then see how the mechanical intelock of the units power cord and the switch that it activates comes into play.


Consult the supplied mark-up and you will see the 6 batteries that can power your set, located at the right bottom corner, in series, they will then supply 9 Volts.

Your MAIN switch, on the end of the sets volume control is being a double pole single throw type which uses marked section B to switch the PINK battery power to the radio.

Additionally note that there is ALSO being a series interlock switch in that circuit . . . which is being denoted in BLUE .

That interlock switch is always being mechanically closed IF the AC power cord is not plugged in, so that as soon as the volume control is advanced and the MAIN A-B switch closes both of its contacts the radio plays from battery power, passing through the PINK markup.

Should you want to operate the radio on AC line voltage, as soon as you plug in the AC line cord it physically pushes the interlock switch open, so that the battery is isolated and that the switch is open as the schema is currently showing..

The incoming AC power is stepped down and rectified to supply your 9 VDC through the RED block route and passes through the RED A section of the MAIN power switch to power your radio from AC power while totally isolating your battery, out of circuit.

No operation on battery power again until you unplug the AC cord from the radio to disengage the interlock switch.

Gloria . . .ohhhh . . . . GLORIA . . . . G . . . . L . . . O . . . R . . . I . . . A



YzARIRm.png


Got it ?

73’s de Edd
 
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Richard9025

May 24, 2016
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Hi Edd !
Yes I got it !
Additionally note that there is ALSO being a series interlock switch in that circuit . . . which is being denoted in BLUE .
Yes , it works just like you explained
The interlock switch :
interlockswitch.JPG


So , the red line is the rectified +9vdc from the bridge rectifier
This red wire comes from point 41 and goes to the A section of the switch , to pin 2 in the diagram of your post :


41.JPG


A representation of the wiring (done by me , the previous owner messed up everyting) :


gloria4 1989 - Copy - Copy.jpg

BUT :

I think I mistakenly made a solder bridge across the red wire (or something connected to it) and the negative terminal of C420 (or something connected to it) , because if I hook the pink wire to point 41 (with the radio connected to a 9v battery , tuned to a local radio station) , it makes a spark ------> it shorts (it shouldn't!) ((and it stops working, of course)) so that's why if I connect all the wires like in the representation up above , it doesnt work , only if I remove the red wire ...(that goes from 41 to pin 2 of the dpst)
I'll check the solder bridges .

Gloria . . .ohhhh . . . . GLORIA . . . . G . . . . L . . . O . . . R . . . I . . . A
 

73's de Edd

Aug 21, 2015
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Sir Richard:

Praise be to you ! . . . For your additional supply of a greater definition snippet of the 'ole Gloria units schematic.

Simplified Power Supply Schematic:
28G0Ocb.jpg


They used an INORDINATE number of LIKE dashed lines across the very bottom of the drawing with varied dashed markings interpretations of:
  • Separation of power transformer area
  • Separation of a shielded area
  • The “star ground” shield connection of the volume control
  • The mechanical to electrical relationship of the power cord being plugged in, to activate
the interlock switch to separate battery power sourcing.
Those dashes have now all been omitted for less schema clutter, with only the + DC power input at Buss 40 and the Negative ground at Buss 43 that runs all across the schematic.

Now you are questioning the correctness of the schematics power supply, but it is correct, it is just designed in a manner unfamiliar to you .

I call it an “ upside down and backwards circuit “, as you are most commonly seeing a linear design power supply, initially taking the + output voltage and then passing it through the collector to emitter of an NPN power transistor with any regulatory control introduced at the base.

Not so on this unit, they are delivering the + output of the power supply directly to the radio.

Any voltage correction or ripple filtering due to heavier current demands are being corrected by a PNP transistor placed between the ground return of the radio through the emitter across to its collector which finally connects to the negative of the Full Wave Bridge. That then completes the power loop.

You have fathomed the operation on battery which has its only quirk in the fact that the AC line cord needs to be unplugged from the radio to mechanically flip the interlock switch so that the interlock switch at the right corner of the schema goes to its electrically closed state.

Negative of the battery gets up to 44 which connects into the radios common ground buss at 43.

Positive of the battery passed thru a closed interlock switch to encounter a closed power switch and power passes up to 40 and above to power up the radio.

The last thing that is going to look normal to you is being the C418 1K / 16VDC electrolytic that has its + connecting to 40 and its – connecting into the 43 buss.

However, another thing that will also look normal to you is the C421 elect of 1K / 16VDC which gets its negative lead connected to the – of the FWB and its + connected to the 40 buss and all the way back to the + of the FWB along with the main + power on up into the radio.

Your T16 power regulator transistor is now needing base bias to conduct and provide a completion of its emitter, connected into the main minus buss of the radio at the GREEN oval, and completing a negative power loop to the – of the FWB.

That is being provided by the R428 thru R427 feed into the base with an intermediate picking up of some regulation from Zener D7.

Now if your C420-C418-C419 are still holding up after 50 years you should have a good working radio.

Remember this is a linear power supply using slow undulating 50 or 60 ~’s . . . not some new generation switch mode supply that has its electrolytics being jack hammered to HELL by constant HIGH level square waves / pulses hitting them at 20-200,000 times per second.

If your radio gots hummmmmmmmmm then confirm your having a good C420 and C418 and then lastly, the MIRACLE capacitor C419.

If the radio is working at low levels and starts getting hum and distortion as the volume is advanced , with a increased and resultant power drain on the power supply.

It seems that your glass smooth sea of DC power is getting pulled down and a tip of a boulder is starting to show up (ripple).

The transistor base immediately detects that change at the base and it ups the conduction of the transistor to bring the DC up to correct and get out of the onset of ripple and back into a smooth sea of pure DC again.

Wonderful thing happens here . . . that amplified correction by the transistor . . . ends up making that capacitance effectiveness being tremendously enhanced.
If you are having that 220 ufd capacitor and the amplification factor involved with a Beta / DC gain of the transistor, it would then be producing the effective filtering effect of a 2200 ufd capacitor if the transistor had a Beta of 10.

Now . . . you additionally know about the units capacitance multiplier circuit’s functioning.

All 3 electrolytics put together can potentially give you in excess of 4000 ufd of filtering . . . wheeeeeew.

With all functioning properly , this power supply should be about as quiet as a baby mouse
urinating on a cotton ball.


Thassssit . . . . .

73’s de Edd
 
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Richard9025

May 24, 2016
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Very good explanation of the circuit !
If your radio gots hummmmmmmmmm then confirm your having a good C420 and C418 and then lastly, the MIRACLE capacitor C419.
Even with replaced capacitors it gets : hummmm ,it is present all the time at all the volume levels .

I saw a jumper wire poorly soldered on the circuit board and wondered .. why is the bridge rectifier soldered UNDER the board and not in his place ? and why is that jumper wire connecting the - of the bridge rectifier to point 43 ...
So , I made a drawing of what ACTUALLY is in this radio
wrong wiring - Copy.jpg
High quality : https://goo.gl/photos/Dj7Bbq1LuuGz5y6B8


Read the notes on the image !

You can see that the bridge rectifier is mounted BACKWARDS ...
That diode (D???) just delivers the pozitive current to both leads of C420 and C419 , I wonder how that transistor is doing now that it has pozitive current on its collector and base
I checked two times if this drawing is as it actually is in the radio and it clearly is ...
All 3 electrolytics put together can potentially give you in excess of 4000 ufd of filtering . . . wheeeeeew.
I think that now only C418 is filtering ..
What should I do to reverse what this person did ?
Now I know why the radio wasnt starting if I connected the yellow wire , it would short ! , the pozitive from the D.P.S.T power switch and the negative from the bridge rectifier and the rest of the circuit (on batteries)
And it isnt that old , it is from 1989 (the first models came in 1972 , they had germanium transistors)
 

73's de Edd

Aug 21, 2015
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Red wire needs to be removed, the yellow is OK, then you need to reverse the polarity of either the output of the FWB or the set of 4 individual diodes being used for building a FWB up.

Just a moment . . . .BAM M M M M . . . a fast wave of the magic wand, along with an accompanying swirl of some resultant smoke, and we have the age of the relic now being reduced to only 30 years
After making the suggested above changes you might also check the C to B to E health of the PNP regulator pass transistor .
And if you are doing a quick power up evaluation, also check the voltage being read across Zener Diode D7 .

Thassssit . . . .

73's de Edd
 
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Richard9025

May 24, 2016
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Red wire needs to be removed, the yellow is OK, then you need to reverse the polarity of either the output of the FWB or the set of 4 individual diodes being used for building a FWB up.
Good , I'll do that after I figured out this 45 year old transformer https://www.electronicspoint.com/threads/transformers-terminals-according-to-the-schematic.283575/

After making the suggested above changes you might also check the C to B to E health of the PNP regulator pass transistor .
This old chap (T16) isn't doing so great :
sprdsheet.jpg

And if you are doing a quick power up evaluation, also check the voltage being read across Zener Diode D7 .
Do I need to also move that diode where it should be ? (between R428 and R427)
 

Richard9025

May 24, 2016
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OK , so I reversed the polarity of the full wave bridge rectifier and cut that red jumper wire just like you said
Also I disconnected the wire that was bypassing the fuse and put a new 1amp fuse in the radio
And checked for shorts , all looks ok
Then I powered it up , it received the radio post very good but it buzzez
BUT
it isnt the same buzz that was when I got it , it is a little-high-pitched and louder buzz that stays with th volume , when i increase the volume , the buzzing increases
So then I checked the voltage that was coming out of the transformer : ~15-16 V AC , and it should be 11,5 VAC .
The voltage across the pozitive and negative terminals of the bridge rectifier : 16,5 V DC
So ,this radio is running approximately on 16 V DC when it is plugged in the wall outlet . (no wonder why the transistors just gave up after 2 days of use)
On batteries , 9VDC , it works flawlessly .
I think this buzz is caused by OVERVOLTAGE , how can I get rid of it ? (maybe a resistor in series or someting like that ?)

Also , I read on some forums that in this radio , the usual problems are the electrolitycs (replaced almost all of them) and the ceramic capacitors (47nf) that should filter the noise , that may cause the buzz , I'll replace them (and add one because one is missing)
 

73's de Edd

Aug 21, 2015
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Looking at your actual schematic of the found wiring / circuit conditions in your radio, by referring to post number six .There is being no Zener diode at the junction of the 220 and 1 ohm resistors, therefore your collector to to base route is turning T16 transistor FULLY into conduction and there is being no voltage reduction / regulation.
Do you have any zeners available in stock / scrap that fall in the 6---12volt range?
OR . . . .do you know how to test the " misplaced D??? " to see if it could be our misplaced D7 ?
Or is it physically possible to install each of the batteries backwards in the battery holder , so that we could get a temporary minus 9 volt test voltage reference ?

73's de Edd
 
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Richard9025

May 24, 2016
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There is being no Zener diode at the junction of the 220 and 1 ohm resistors, therefore your collector to to base route is turning T16 transistor FULLY into conduction and there is being no voltage reduction / regulation.
Yes

I desoldered the D??? and identified it , it is a PL12Z zener diode , it is the diode that appears in the schematic
So this D??? is our D7
Also I see that there is a tracer broken (it was heated too much) . That tracer made the connection of the pozitive of C419 and the cathode of D??? to the rest of the pozitive bus : So long story short - C419 and D??? werent even conneted to the circuit !

The transformer is not the original one , in 1989 there was a shortage of electronic components in Socialist Republic of Romania and they used in this set a 16,5V AC transformer

Or is it physically possible to install each of the batteries backwards in the battery holder , so that we could get a temporary minus 9 volt test voltage reference ?
I can but I don't wanna see capacitors exploding .
 

73's de Edd

Aug 21, 2015
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Sir Richard:


OK . . .then . . . if D7 tests good, proceed in installing it where it belongs . . . with PROPER polarity.

And if you have changed C420 and C418, hopefully they were 25VDC rated, talking care of our inherently higher transformer voltage, all will be well.

Won’t need to resort to the batts, but that would NOT have been a problem, since the AC line was to be left plugged in, thereby switch isolating them from the circuitry.

See if that thing will now flip, flop and fly !


73’s de Edd
 

Richard9025

May 24, 2016
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So with the zener diode in its place and the solder bridge corrected I get NO BUZZING
Across C420 I get 17 V DC , and the capacitors are for 16 V DC , that should do it ?...
And if you have changed C420 and C418, hopefully they were 25VDC rated, talking care of our inherently higher transformer voltage, all will be well.
They are 1000uf/16V but I have some brand new 1000uf/35V (got them for recapping another radio)

Across point 40 and the negative bus of the radio I get 10 VDC , so the transistor does its job

So should I change these 1000uf caps ? I dont think 17 volts on 16 volts capacitors is such a big problem
 

Richard9025

May 24, 2016
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Replaced the 16V caps with proper 35V
Now the radio works very good , without any problems !
Any suggestions before I put it to an endurance test ?
Thanks !
 

Richard9025

May 24, 2016
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After 1 and a half hours on batteries it worked very good on all bands
but
After 30 minutes on 220vac , it developed some big problems
On Long Wave , it receives almost nothing
On Medium Wave it receives images of radio stations and when I reach the middle of the band , it starts buzzing , making very high pitched noises and all sorts of hums and strange noises
On Short Wave 1 it works ok
On Short Wave 2 it receives only distorted images of radio stations
And on fm it receives images (like it should receive , it works on the old eastern band OIRT 65.8 to 74 MHz)
Also , when it is connected to ac line , it pops everytime , popping every 2 secons or when i rotate the volume/tuning or when i touch the antenna but after 30 seconds that popping disappears (on batteries it doesnt pop)
Yeaaa ... It really doesnt like its power supply
 
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