Wondering if anyone had ever seen the diode symbol in the pic below at d105. I've never come across it and found it odd enough to want to create an account and post it see if anyone else has ever seen it this is on a pioneer laser disc player probably from the late '80s early '90s that I'm playing with just as a project. Text on the board clearly she says that it's a diode but when I run it through my tester it seems blown showing up is just a resistor of about .3 ohms. I'll post a picture of the diode as well.

 

Just a guess. Perhaps a dual Zener diode? Can you post the part number on the package?

 

Just a guess. Perhaps a dual Zener diode? Can you post the part number on the package?

S kv695. The S looks like a symbol of some sort, pic attached. The nine and five have a line over them.

 

S kv695. The S looks like a symbol of some sort, pic attached. The nine and five have a line over them.

In tried testing it with my semiconductor tester but the part is failed and shows is a resistor of about .01 ohm (short)

 

Its a Transient Voltage Protector ( back to back Zenner diode). Come in a range of voltages. If shows as a short it has done its job, they are a protection device against HV spikes.

 

Ah any advice on figuring out reasonable values for replacement component? Measure voltage across those two points with it removed ?

 

One idea. If it is a protection device, the circuit might very likely work without it. Not protected but functional. Have you tried operating without it?

 

Looks like your board is the power supply from the laser disk player.

PIONEER DVL-919,DVL-909,DVL-91,DVL-90 Laser Disc Player Power Board VWR-1286 | eBay

Here is the schematic of the VWR-1286 power supply board with D105 showing with the same schematic symbol. Looks like what debe sez.

Pioneer DVL-919 Service Manual (Page 36 of 89) | ManualsLib

Here is a discussion about a shorted D105

power supply for the DVL909 pioneer helpppppp (google.com)

As I speculated, try running without it.

 

If it runs without the part and you must have protection, plug the unit into a power strip with a surge protector.

 

Ah excellent info thank you very much, I managed to track it down with a multi meter initially and circuit looks good from an ohm perspective with it removed. Once I get a new fuse and don't other bits we'll find out.

 

Thanks very much, I found a manual but it left out d105 or I was looking at the wrong schematic version lol.

 

It apears the original UK1V26 is only 265V TVS & was a problem. Sugested size is P6KE350 TVS diode as a replacement.

 

I had a TVS failure in a TV set many tears back, and not realizing that was what popped the fuse, I replaced the fuse and it immediately popped again. That time the TVS also showed signs of failure, and after I traced it out in the circuit, I removed it and the TV worked quite well as I was unable to locate another TVS device locally.
Several years later another line transient took out the CRT high voltage regulator, and so I used a 24 volt transformer in an auto-transformer scheme to run the set on 95 volts, which did not trip the over-voltage circuit. We used that for several years.
My point being that a TVS can be helpful but they mostly seem to protect by latching in the shorted circuit mode.

 

That looks like exactly what happened here. With it installed the entire primary side resistance reads around .8 ohms, removed it's around 1m ohms.

 

Vishay purchased General Semiconductor's TranZorb line. Littlefuse lso picked up some. Part numbers with a C on the end are bi-directional, for AC applications. TP5K, TP6K, and TP1.5K are the most common through-hole parts.

https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode

https://www.littelfuse.com/industries/automotive/semiconductors/tvs-diodes.aspx

Here is waaaay more than you ever wanted to know about them.

http://www.reallyreallyrandom.com/zener/media/Zener_Theory_and_Design.pdf

ak

 

Thanks for the help all, still trying to find something available to replace it. I do have some 300 watt unidirectional tvs diodes, can I just solder two of them together and get the same effect?

 

Thanks for the help all, still trying to find something available to replace it. I do have some 300 watt unidirectional tvs diodes, can I just solder two of them together and get the same effect?

NO!! Not unless the voltage rating is correct.
I have not seen any verification that the device that the TVS was in still is functional or not.
With the TVS removed and the device assembled, and the fuse replaced, the TS should be able to verify that it operates correctly. If it DOES work right, then it is worth the effort to replace the device, if not, additional diagnostic effort will be required.

 

I haven't tested the full device yet but the tvs was bad. With it removed it draws almost no current, with it installed it good to the limit on my current limiter. Without the limiter it blows the fuse with the tvs installed. I'll throw it back in and test.

 

There is no reason to test with the failed TVS device in place!!
The TVS is a protection device, not an active component. So I was, and still am, suggesting checking with the failed TVS disconnected. I anticipate that the operation will be satisfactory.

 

Ah any advice on figuring out reasonable values for replacement component? Measure voltage across those two points with it removed ?

It's best to trace out the circuit around the area you found the TVS diode and look for what it was protecting and limit the voltage based off of the datasheet for the protected component.