My little Sony has arrived;
Looks intact, mains lead chopped.
No raster but line timebase is running (I can hear 405), initial investigation shows that tube heater is not lit.
No raster but line timebase is running (I can hear 405), initial investigation shows that tube heater is not lit.
Is there any sound? It looks like the CRT heater comes directly from the 12v rail. Could just be a faulty connection.
To understand the black art of electronics is to understand witchcraft. Andrew.
Sony manual is in the library, for the benefit of those without access, here is a circuit snippet.
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
If it's anything like my 9 inch Zenith the CRT heater lighting is very hard to detect. I could barely see the heater, but the set was giving a nice bright raster so no worries about the CRT. I would check for heater continuity. As was previously mentioned, these CRTs run at 12 volts straight from the main DC supply line.
Pins 3 and 4 carry the filament supply. Check for 12V when in operation, check for continuity ( a few ohms) between the pins. If the multimeter stays on OL then unfortunately you may have a dead CRT. If you do have continuity and voltage, then it looks like you will have to look at the drive to the LOPT. It sounds like you've got line whistle (10.125kHz on 405 lines). This indicates that the LOPT may be ok. The next thing to check would be the EHT which should be around 10kV for a CRT this size. You will need a high voltage probe (e.g. Fluke 80K-40 or similar and a 10 megohm meter)to measure this. If there is EHT then look for cathode train faults. The cathode (usually pin 2) may be biased high thus preventing electron emission. Then you will have to work your way back through the video output chain (best done with a signal generator and an oscilloscope). I hope that this helps. I'm just starting out here in the world of televisual electronics, but watching the youtube professionals such as shango066 has given me some ability to fault find.
As it is, the CRT may be replaced easily with a more modern unit, if it is the filament. There are a few sellers selling these for £50 or so on ebay; if you want the correct phosphor (white) make sure that the phosphor is P4 (although, as I will testify, P31 gives a pleasant green and watchable picture), and P3 is amber.
Other major parts such as the LOPT may be much harder to find, due to the dual-standard nature of this set. However, it will be worth checking that all the connections are sound and that there are no dry joints on the PCB.
A bit more investigation revealed no volts at the filament, the single wire from a 12v tag had come adrift. Fixed that and tube heater on, and a picture.
You have to admire Japanese workmanship, a TV as old as me, obviously not used for years and it's more or less OK ! I was surprised that the was no other damage, as although the set was double boxed, there was no cushioning at all. After hoovering out all the dust and cobwebs, finding a length of mains lead was more of a problem than I thought. Three core small enough to fit the hole was a bit difficult to find, I eventually got some rubber covered from Screwfix, I was surprised that the chassis was earthed, I've never seen a portable of that era with a transformer PSU with an earth.
Time to give it a clean tomorrow and hopefully get some 405 pictures on it.
I think these must be among the few vintage sets you can just plug in and use almost without a second thought.
Watch the red outlet connection on the LOPT to the EHT stick-diode.... I foolishly touched mine and got a bit of a sharp tickle.
To understand the black art of electronics is to understand witchcraft. Andrew.
Posted By: mfd70
[...] I've never seen a portable of that era with a transformer PSU with an earth.
A transformer allows the set to run off low voltage DC allowing it to be run off a car battery or the special Sony battery pack. Many subsequent set designers used this method in 12 inch portables as this was the easiest way to implement AC/DC operation.
I'm glad that the fix was simple. Quite often sets have gone into storage with simple faults like this! Shango066 has resurrected abandoned desert sets where the fault was a simple wire disconnection! It sort of makes you think how durable this technology is.
A bit more cleaning of the cabinet today, some vinyl and rubber restorer brought up the plastic, the front plastic is a bit scratched, but a few goes with RS abrasive polish has helped.
Interesting to note there are a few ISO symbols to warn there are metric screws used throughout, these are also JIS head.
Good pictures on 625 and 405, I'm surprised at the UHF and VHF gain, these pictures are just with the internal aerial and about 6 inches of wire connected to the signal generator just out of shot.
An excellent little TV !
I have two of these. Just powered one up a few weeks ago. Brilliant CRT.
Do you also have the front plastic cover for yours?
I have one cover but the other one was missing from the set when I got it.
Andy
