WSR7-l6 with blown F1 fuse from a Seeburg R

Recently picked up a Seeburg R. Receiver is out of cabinet. Noticed F1 fuse was blown (a 4 amp was installed). Would like advice for testing T1 and T2 transformers before installing new fuse and plugging in. Will measuring the resistance of primary and secondary windings reveal the issue if the blown fuse was caused by a transformer?
Thanks, Steve.

A simple "ohms" test of transformers will not reveal if they have a shorted turn in their windings, rendering them defective.
Unloaded, with a current monitor attached, they should draw very little through them, and remain relatively cool.

Concerning the blown fuse - what value is stated at that location? - replacing with improper values is pure stupidity and dangerous.

As is usually the case, components "down wind" from the transformer are usually the culprit, and then proper troubleshooting with the service manual is in order.

Guys,
"F-1" is marked as a 5 amp FB fuse-- This fuse is on the primary side, of the transformer, so ANYTHING, on either side. could have caused it to blow--including the fact that it was undersized (altho, I doubt that was the cause). I would use a metered/fused power supply, and probably a an incandescent lamp in series with this WSR on power up--with nothing connected to the WSR--Ron Rich

Steve_B wrote:Recently picked up a Seeburg R. Receiver is out of cabinet. Noticed F1 fuse was blown (a 4 amp was installed). Would like advice for testing T1 and T2 transformers before installing new fuse and plugging in. Will measuring the resistance of primary and secondary windings reveal the issue if the blown fuse was caused by a transformer?
Thanks, Steve.

Steve, the main fuse (F1) is only for the primary of T1 -the tran that supplies the machine mech and tube heaters.
T2 is just for wallboxes and it is fused in its secondary. Unless someone changed the wiring, it can not blow the main fuse.

A simple test for T1 without anything connected to the selection receiver is to place a 1 amp-slow fuse in the receptacle and plug it in. With no loads on the tran and no internal shorts in it there should be only slight eddy currents that are well under 1 amp (probably below 1-1/10th amp).

If the fuse does blow or the tran smokes there is either a short external to the tran, or inside it. Either way, any smoke a transformer requires that it be replaced.

If the fuse does not blow use a schematic to start reading voltages from the secondaries. Pay particular attention to the low-DC winding connected to the bridge rectifier and be sure to replace the small filter cap associated with it. FWIW: I have always replaced the selenium rect with a large capacity diode package (around 20 amp@100 volt). Early-on, several of the selection units I bought had bridges that tested Ok in no-load but broke down to approx half voltage when loaded. One danger here is that the low-DC is used for the timing relay in the credit unit and if it is low the machine can get stuck at the write-in point and leave both credi subtract and scan coils energized leading to their overheating and possible burnout.

Rob-NYC

Rob,
You are incorrect--that fuse also "protects" the AC supply to the interior lamps, the motor and the (aux) power supply socket. I have seen all of them cause the fuse to blow--- When I refurbish a WSR or a TSU/TSR, I usually separate the AC feeds and fuse the transformer, itself, at 3 amps--Ron Rich

Ron, he stated that the "receiver out of cabinet" and I said 'with nothing connected to it".....

FWIW: I agree with you on fusing the tran. My approach is to fuse everything coming out of it.
This has already saved several trans when shorts occurred in coils in the credit units and pop meters
I use:

Low Dc: 1 amp fast
25Vac: 4A/slo-
5VAc: 3A/slo (IIRC)
Tube heaters:5A/slo This is a 3.2 amp load.
150Vac (2050 plate) ½A/fast.

As Ron suggests, using a light bulb in series with the input is an excellent way to limit current. With nothing connected to the unit I would expect a 15 bulb would show only slight light -if any. This is also good for limiting current and preventing the waste of fuses while you remove loads if a short is detected.

Rob

Hi Rob,
I had a TSR once, that had an internally shorted "110 volt,lamp plug", that would blow the primary fuse, when NOTHING was plugged in-that one took a while to find ! I agree with your secondary fusing, except for the 24 volt AC fuse size. I use a 3 amp fast blow there, and also fuse the pop meter ( and cancel coils, if used) on the mech at 1/4 to 1/2 amp SB. Ron Rich

I agree with your secondary fusing, except for the 24 volt AC fuse size. I use a 3 amp fast blow there,

That would be fine on the older E-M machines, but not on V-VL-K due to the drum which draws just over 3 amps.Add that to the latchbar and right away it pops. This is a robust winding and a 4-slo has been effective in my experience.....Why Seeburg didn't fuse these things adequately when all the other manufacturers did a reasonably good job is another matter.

Rob

Rob,
To answer that question--IMHO, they either "paid someone off", or "had someone in their pocket"-- this "caught up" to them starting with the LPC run, and for many years after---as UL required them to use those expensive "red caps". They fraught that ruling for years--got out of it about 1977 -- Ron Rich

Ron, as a kid I used to hang out in the many repair shops in this neighborhood. I'd take home stuff that people didn't want to pay to repair and abandoned at the shops.

Looking back at what was the state of consumer electronics back then the casual attitude toward safety was appalling.

Cheap radios, phonos and even some TV's with hot chassis and only plastic knobs between you and the line. Zero fusing even in cases where the internals were open-pan and right next to wood cabinetry. Yet, there are still jackasses who bray about the "EPA and Osha" and other safety organizations.

Rob

Hi Rob,
I am one of the "jackasses" who bray against OSHA, and the EPA, when I feel that they are being unreasonable, or "jackasses" them selves.
Yes--some of the regulations, are/were necessary, but they tend to go way beyond that at times !
I have had them "force me" to do very stupid things that once done, even the next "inspector" to come along, has scratch his head about !
Others have been very reasonable, and most would at least explain their thinking, and give me the chance to explain why something should not be necessary. Most of the time, they would keep an open mind, and agree with me when I explained what I was thinking.
My neighbor, owned the last plating company in San Francisco. He was ordered to spend well over 1/2 million dollars to "upgrade", if he wanted to continue operation. He agreed, and was given a two year time period. He did EXACTLY everything as per agreement, but when the (new) inspector came to sign it off, he did not approve of what the former inspector had agreed to, and insisted that my neighbor spend another 1/4 million dollars, in the next 6 months. Guess what-yep, he closed the shop, and sold the building/ land to a developer, on the date that "order", was to be done. Ron Rich

Rob-NYC wrote:Ron, as a kid I used to hang out in the many repair shops in this neighborhood. I'd take home stuff that people didn't want to pay to repair and abandoned at the shops.

Looking back at what was the state of consumer electronics back then the casual attitude toward safety was appalling.

Cheap radios, phonos and even some TV's with hot chassis and only plastic knobs between you and the line. Zero fusing even in cases where the internals were open-pan and right next to wood cabinetry. Yet, there are still jackasses who bray about the "EPA and Osha" and other safety organizations.

Rob

Those "cheap radios" etc that were hot chassis, were series-string filament type sets.
And relied on a small "fusible" resistor and split rectifier filament as the "fuse" device.
If a fault should happen, it would simply take out the recifier heater and or the surge resistor.
Cheap, but effective.

Thanks to all for the advice. I tested the receiver as suggested, using a 1 amp slo-blo fuse in F1. With no load on the receiver the fuse did not blow and I did not see any smoke. I let the receiver run for a while then checked all the voltages at the transformer secondaries. All were slightly higher to posted specifications in the schematic, as was the line voltage, so I considered the values (and transformers) to be good. However, I still will need to identify why there was a blown fuse at F1 when I received the unit.

I do have a question as to which cap would be the small filter cap associated with the rectifier. Could you please identify it for me by its value on the schematic. I have replaced all the caps but would like to identify it.

Thanks again,
Steve

Steve,
Before inserting all plugs, check the ones for the mech and keyboard that SHOULD have the plastic "indexing key" in the center--these often are missing causing "someone" to plug them in incorrectly, thus bowing a fuse (YOU HOPE !). Leave a small fuse in the unit, and use a lamp in series as you plug one plug in, at a time--Also-remember that the Amp is also connected to that fused line --
The -25 volt filter cap is the 25 mfdx50 volt POS grounded cap near the 2050 tube socket-- Ron Rich