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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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27th Mar 2017, 7:11 pm | #1 |
Pentode
Join Date: Jul 2005
Location: London, UK.
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Deciphering resistor value in McMichael 365
Evening All
I'm repairing a McMichael 365. Some of the resistor values have drifted by 50 to 80%. In addition, a few resistor values are a bit hard to decipher from their colour code. For example, the one on the first picture is meant to be a 500K according to the schematic and manual? In addition, this is not helped by the fact that some of the actual wiring around the detection diode resistor load appears to differ from the schematic. It seems i'm experiencing exactly the same anomaly (or feature!) as mentioned in the following post. I'm wondering if McMichael had actually made a revision to their original schematic drawing ? https://www.vintage-radio.net/forum/...d.php?t=105570 Would you know how to decode the resistor values on these pictures? The dog bone resistor of 2.2K also seems of a different value compared to the cathode bias resistor R5 of V3 which is meant to be 1350 ohm. The photos of the above post also appear to be using the same original component which re-inforces the fact there may have been a second revision of the schematic/manual? Thanks Thierry
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27th Mar 2017, 7:18 pm | #2 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
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Re: Deciphering resistor value in McMichael 365
Thierry,
They look like body/tip/spot resistors (even though this one is banded) - so your body green 5, tip black 0, yellow spot multiplier 0000 = 500K. Andrew
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27th Mar 2017, 7:18 pm | #3 |
Dekatron
Join Date: Apr 2011
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Re: Deciphering resistor value in McMichael 365
As a guess:
1st pic 500k. 2nd pic, not sure about the dogbone but possibly 2.5k if there's no body dot, the other two, 120k 3rd pic, 3 meg ohm. Lawrence. |
27th Mar 2017, 7:43 pm | #4 |
Dekatron
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Re: Deciphering resistor value in McMichael 365
What Lawrence said
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27th Mar 2017, 9:22 pm | #5 |
Pentode
Join Date: Jul 2005
Location: London, UK.
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Re: Deciphering resistor value in McMichael 365
Great, thank you.
Something else i would like to ask regarding this set. Does the motor or its mechanical parts require any particular maintenance e.g. oiling, etc ? Thierry
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27th Mar 2017, 10:31 pm | #6 |
Dekatron
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Re: Deciphering resistor value in McMichael 365
The two similar ones look more like 12K to me, but if 120K makes sense in the circuit then OK. Check them?
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27th Mar 2017, 11:15 pm | #7 |
Hexode
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Location: Welwyn Garden City, Hertfordshire, UK.
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Re: Deciphering resistor value in McMichael 365
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28th Mar 2017, 9:37 pm | #8 |
Dekatron
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Location: Leominster, Herefordshire, UK.
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Re: Deciphering resistor value in McMichael 365
Hmmm... let's put it down to my monitor- they looked more like brown red orange to me.
Would yellow fade to orange or vice versa I wonder?
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31st Mar 2017, 9:28 am | #9 |
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Re: Deciphering resistor value in McMichael 365
I put mine back to the configuration according to the circuit diagram and it works well now if maybe a little lacking in bass response. I eventually cleared up the hum from the smaller speaker by substituting a 10H inductor.
I completely stripped the motor and deck as the original lubrication had gone solid. Fortunately, being a single play unit, it is very simple. The rubbers in the pickup head were also solid. There is lots of information here about this. For the pivot rubbers I discovered that you can still get bicycle valve rubber tube on ebay if required, but in the meantime I had bought some Fladen traditional float rubbers which were recommended and they also work well.
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