Radio Newbie in need of some guidance for an 84
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The plot thickens! You should not have 0 ohms between 6 or 7 to 8. You also reported the center tap (8 ) to chassis as 0. As indicated this should be around 320 ohms via the resistor off the CT to chassis. Makes me think as indicted to pull the transformer wires off the chassis for the 5V line, the HV line and the center tap and make readings from the various to their partners and also to chassis ground to see if we have an internal short on the transformer and all the windings are intact. I suspect some wires messed up or the transformer. Once you identify each winding and confirm continuity also do a check between the 5V winding and the HV winding to assure no short between the two.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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I have disconnected all wires from the transformer. Readings as below
9 & 10 = 416
9 & 8 = 200
10 & 8 = 216
3& 4 = .6
3& 5 = 0
4& 5 = 0
6& 7 = .6
7 & 8 = 0
6 & 8 = 0
Seems the center taps are the problem for the filaments. ?????
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I think your right, looks like a short between the HV center tap and 5V filaments. With the wires still free, check from 8 to chassis and from 6 to chassis. How do the wires look coming out of the transformer? Good solid insulation? It is possible the wires are shorting together inside the bell. Next step would be to remove the transformer and take off the end bells to review the internal connections.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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6 & 8 to chassis = 0
Will remove the bells and see whats going on. Be back.
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The diagram I have for the transformer shows 10 wires. I only have 9. I assume that I do NOT have a 5(Center Tap)
I have two WHITE wires which assume to be the Primary. One goes to the on/off Pot.. the other goes to the other end of the power cord.
Putting the meter between these two white wires, I have continuity and about 9.9ohm.
Testing capacitance between the Center Tap(-  and 3, 4, 6 & 7 , I get 1 nF
Pictures below
https://pbs.twimg.com/media/B7LTz_uIcAE2kDs.jpg:large
https://pbs.twimg.com/media/B7LT3bYIQAAAyMR.jpg
(This post was last modified: 01-12-2015, 03:37 PM by rciancia.)
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Not good pic on my I phone looks like its Burt a little and some one splice wires already
In service page think philco eliminated a wire
Some day, and that day may never come, I will call upon you to do a service for me. But until that day, accept this justice as a gift
mafiamen2
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The wires are not spliced. Someone put heat shrink tube on the wires where they exit the transformer. I can feel the wires in there are smooth.. no solder joints. The unit is not burned, but I do see some melted wax on the inside cover. Unsure that was as a result of my problem or is causing the problem.
Either way, both sides of the power inputs are NOT equal to the CT, so something is not right with the transformer. I also have continuity between the two power leads(1&2) unsure if normal.
I found someone selling the same one for $15 and ordered it. It is said to be good so will check it out when it arrives. Hoping that solves all my problems here. Will keep you posted on progress in the next few days. If anyone knows someone who can rewind my transformer I think it is worthwhile to do so.
(This post was last modified: 01-12-2015, 07:57 PM by rciancia.)
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Actually the resistance to CT from the legs of the HV will not be the same due to the way the coil is wound. The voltage out should be close to the same. Primary looks good. Shorts to ground look BAD. You found a fair price for a replacement. Having yours rewound professionally your probably looking close to $100.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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From a post on the alternate forum it appears there is a real question as to what constitutes "0" ohms in the OPs reports, open or short? Need to know measuring equipment and interpretation of results. Makes a bit more sense if it means open or infinite.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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I am using a digital meter and have the meter set to OHMS. I've adjusted the scale as required and the result is simply 0 Ohms.
Without applying power to the transformer, is there a better way to test it ?
thank you Jerry
https://pbs.twimg.com/media/B7OZ-7MIAAAHi4q.jpg
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Sounds like you were measuring correctly and 0 ohms to #8 is not good. I had to bow out yesterday for work, but Jerry gave good advice and $15 for a transformer (if it is good) is a very good deal. Take some careful resistance measurements when it arrives, especially from # 8 to 6 & 7 to verify it isn't shorted. Hopefully that will get your little 84 playing again... good luck!
John KK4ZLF
Lexington, KY
"illegitimis non carborundum"
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To close the loop on this here is what I measured and how I did it.
I removed the Transformer from the unit entirely, and measure across the following with an OHM Meter.
Primary 1 to Primary 2 = 9.8 ohm, meter beeps indicating continuity.
Filament 3 to Filament 4 = 0.5 ohm, meter beeps indicating continuity
80 Filament 6 to 80 Filament 7 = 0.4 ohm, meter beeps indicating continuity
80 Plate 9 to 80 Plate 10 = 416 ohm
80 Plate 9 to Center Tap 8 = 216 ohm
80 Plate 10 to Center Tap 8 = 200 ohm
Putting Filament pairs 6, 7, 3 and 4 individually to Center Tap have no reading and no continuity beep to Center Tap 8
In your view are these readings normal ?
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Quote: Putting Filament pairs 6, 7, 3 and 4 individually to Center Tap have no reading and no continuity beep to Center Tap 8
In your view are these readings normal ?
Yes, those readings are normal and should be described as infinite resistance not "0". Zero ohms describes a dead short.
Quote:
3& 4 = .6
3& 5 = 0
4& 5 = 0
6& 7 = .6
7 & 8 = 0
6 & 8 = 0
We have been running in circles!
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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I am sorry for that Jerry, all I can do is apologize. I can tell you I am the type of person who learns from my errs and this is no different.
I am very grateful for your help as well as everyone else here.
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No sweat, it's how we learn.
Did you verify wire 8 on the transformer to chassis is 325 ohms and not 325K?
Can you upload a picture that shows the whole underside of the chassis?
John
Las Vegas, NV USA
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