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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 2:34 pm 
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I may be g at the wrong two resistors in parallel as it looks like another set here

Image

and you were right about the old stuff ,,,,,its out
and when I test the new stuff its all in ,,go figure

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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 2:52 pm 
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Location: Gainesville, Florida
close together in the chassis doesnt necessarily mean that they are in parallel. they would need to be connected to the same point on both ends. the color code values and pin locations help to locate on the diagram.
the new film resistors should be within tolerances. yours look to be at least 1/2 watt


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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 4:41 pm 
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blainenbecky wrote:
tubeAMP wrote:
those NOS carbon resistors may be out of tolerance as well. check the with ohm meter. checking resistors in parallel in the amp will not give you singular reading




Roger that and thanks



is this the parallel resistors circled in red bro

Image

the colors on the 2 resistor in the big circle are brn blk yel sil
and the other resistor is red gre yel sil
Image

so if I am reading the color chart right this must be the 2 in question .
I am also guessing when you put the resistors side buy side like that it does the same as wiring caps together and multiply the 2 values into one right? ,,,,,so it could have just as easily have been one 350M resistor in that spot right ??
so I could just put one orange,green and black resistor there and do the same thing right ? or did they use 2 resistors to get more Watts ?


Last edited by blainenbecky on Jun Wed 12, 2019 5:17 pm, edited 2 times in total.

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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 5:14 pm 
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Location: Seattle WA US
Nope. When you parallel two resistors, the resulting resistance is:

R = (R1 x R2) / (R1 + R2)

The parallel combination of your two resistors is 71428 ohms, which would be written 71M in the ancient notation of your schematic or 71K ohms in modern usage.

-Chuck

<edit, corrected my math, I shouldnt be allowed out without my sliderool.


Last edited by K7MCG on Jun Wed 12, 2019 5:49 pm, edited 1 time in total.

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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 5:37 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Gainesville, Florida
unusual diagram using M for thousands. it is a 100K and 250K resistor in parallel. most do not use two resistors in parallel like that. may be for accuracy because there were no 71K resistors ? you need to identify the tube pins to verify connections. try this site below. type in the tube number

http://tdsl.duncanamps.com/tubesearch.php


Last edited by tubeAMP on Jun Wed 12, 2019 7:36 pm, edited 2 times in total.

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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 5:42 pm 
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Location: Seattle WA US
Many companies were still using M=1000 in schematic diagrams and parts lists as late as 1946.

-Chuck


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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Wed 12, 2019 8:17 pm 
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
tubeAMP wrote:
unusual diagram using M for thousands. it is a 100K and 250K resistor in parallel. most do not use two resistors in parallel like that. may be for accuracy because there were no 71K resistors ? you need to identify the tube pins to verify connections. try this site below. type in the tube number

http://tdsl.duncanamps.com/tubesearch.php


In Roman Numerals, 1000 = M. This is likely the reason. It's not really unusual. It was the standard for 1000 on schematics for many years until it changed to K (as already noted in a previous post)

I am NOT an audio expert, but this is a push-pull output and they may have paralleled those two resistors in order to properly balance the amplitudes of the opposing phases into the 6V6 outputs? .... just my guess. The 6J5 is acting as a phase inverter?

cheers


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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Thu 13, 2019 1:00 am 
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thanks for the info guys it is a big help,,,,,,got me a dim bulb tester made today that should be a help when I get the Caps in.

Image

Image


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 Post subject: Re: found an old Gibson Amp can't find model #
PostPosted: Jun Thu 13, 2019 1:07 am 
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K7MCG wrote:
Nope. When you parallel two resistors, the resulting resistance is:

R = (R1 x R2) / (R1 + R2)

The parallel combination of your two resistors is 71428 ohms, which would be written 71M in the ancient notation of your schematic or 71K ohms in modern usage.

-Chuck

<edit, corrected my math, I shouldnt be allowed out without my sliderool.


OK this is blowing my mind a bit ,,,,,I am going to find some vids on youtube to try and get a better grip on it ,thanks Chuck


Well,,,,,,,,,,,,,,edited as I just did some vids on it and Boy my hat is off to you guys,,link to the vid that talks about parallel resistors https://youtu.be/ZrMw7P6P2Gw


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