Like many of us I suspect, over the years I have picked up a few B&W portables. Some I bought because I had one 'back in the day' others because I repaired the model on a weekly basis. Others were gifts or saved from the skip. A few are on the top shelf in my workshop some in the loft and a few in the shed... I have decided it is time I went through them and fixed any faults. A couple may have to go if they are duplicates or rough.
Anyway first is this Hitachi in fetching 1970's orange! The Japanese were never afraid of bright colours it seems! This set came from a friend who thought I would like it, the set was being disposed of many years ago by his neighbour. It has resided in my loft for over a decade so I thought it was time to give it a try.
I plugged it in and switched on. Nothing! I decided to check the plug. No fuse! Put in a fuse and on it came! It's an Hitachi after all. No wonder we didn't see them in for repair, a Thorn 1590 or a ITT featherlight was a much better earner repairs - wise...
The tube warmed up nicely and will probably improve even more with a run, the tuner is a little scratchy as is the volume pot but wouldn't you be after a long sleep? I will remove the back and give it a clean inside and then it can go on the shelf in the workshop for a while. It will replace the ITT which is playing up.
Viva Hitachi!
I just picked this up this morning at the local recycling center, hoping it was a valve set but sadly it's marked solid state on the rear cover despite the red cut out button.
@michael-dranfield that's an interesting set Michael. Not a make I have seen before. It will be interesting to see inside. It does look like it is a UK market model have you any idea of it's age?
not something I have seen before but it looks 70s.@michael-dranfield that's an interesting set Michael. Not a make I have seen before. It will be interesting to see inside. It does look like it is a UK market model have you any idea of it's age?
The Hitachi didn't take a lot to finish it. I bit of a clean out and a clean of the casing. the tuner lost it's scratchiness with a bit of use, I lubricated the drive and recalibrated the inner dial. The vol pot responded well to a touch of cleaner and after checking the LT voltage I put it on the shelf to replace the RGD rapier ( ITT featherlight) which has an intermittent hum bar.
The RGD hum bar problem is a little odd in so much as it isn't heat related. The hum bar comes and goes at random. My first suspect is the bridge rectifier as they always ran quite warm on these sets and were quite a common failing. However mostly the fault was either permanent or occurred after the set had been on a while. The severity of the hum on the picture also changes. Then as quick as it occurred it goes away.
The rect is running warm but I expected that it doesn't respond to being "frezed" though.
I might try a smoothing capacitor first as it is slightly easier to get to...
There were quite a few Sony 9" portables (amongst others) being sold by the Dulwich museum at Punnett's Town yesterday; two 9-90s and a TV110 (the single standard one).
Apropos the hum bar: earthing or a defective riveted terminal on the smoother perhaps? Not being familiar with the set in question my usual line of enquiry is "50 or 100Hz hum?" if the set uses a bridge rectifier.
I've just had two modern SMPSUs through with an identical fault - arcing on the +ve lead where it enters the body of the smoothing cap on the mains side. When I removed both caps, the lead just fell off. Must've been a manufacturing defect.
Note that there is only 1 hum bar.
That means it's 50Hz.
That means it's not a capacitor but one of the bridge diodes.
Replace the 4 of them and you'll be good.
Takes me back! HMV Z1 portables in the early 70s. Very common fault.
@cathovisor I have a 9-90 I bought around 14 or so years ago when I used to go to car boot sales, £5 and it worked perfectly, still does! I have never bothered to get a TV110 I had one as a kid in 1972/3 that belonged to a family member. I remember struggling to find a fault that caused the brightness to decrease, the local TV shop had written it off as a tube fault which it wasn't but it took some finding, not helped by the 'orrid tiny photostat I had of the diagram. Aversion therapy ! It put me off having another!
I think the hum bar is 50 HZ as I only get one 'kink' in each picture traveling down, but I could be wrong. I have removed the capacitor and my thoughts were the same as you maybe the rivets? They look ok though. here is the strange thing, if another 4700mfd is paralleled across the original the fault clears, but if the capacitor is substituted the fault comes back. So I think the cap is innocent, I am now pointing the Anglepoise at the bridge rectifier....
@irob2345 Many thanks for the advice. Our posts crossed, I have come to the same conclusion but have gone the long way around ! Every day is a school day (for me!)
I have a suitable bridge rect in stock I will replace it later today when i return home from my morning errands...
The HMV Z1 used 4 ordinary 1A diodes soldered onto a small PCB that acted (they hoped!) as a heat sink. Pretty marginal, but at the time that TV was being made the component supply position in Oz was difficult.
How about an early 60's all valve portable? Introducing the AWA P1:
One of the better performing portables, rock-solid reliable, simple and easy to work on..
Stabilised scan, DC coupled video and probably the simplest audio amplifier you ever saw.
That certainly is a well built set! One thing that came to mind working on the RGD compared to the Hitachi is how much more complicated physically at least the RGD is compared to the Hitachi. The RGD has A hinge down chassis a separate LT and tuner panel everything mounted on a metal chassis Plugs and sockets to connect it all together etc. Whereas the Hitachi is all on one panel no interconnections on plugs and a simple mount for the PCB. Much easier to assemble and more reliable to boot. Ok it uses a 90 degree (or more) CRT but customers didn't notice or care about the slightly deeper set. It probably used less power at 12 v to run as well....
Anyway I have replaced the bridge rectifier on the RGD with a somewhat overrated one from stock, it runs warm but not as hot as the original, since taking the picture I have added a small heatsink for good measure. The PCB is printed for separate diodes if required but I remember they did run very hot and even became loose due to melting their solder on the ITT sets. I think I have a well cooked ITT version in the shed.
Some final Pictures of the RGD working.
And a Picture of the Sony 9-90 mentioned. There is nothing to do to the Sony, it works faultlessly and is used as a monitor for the 625 and 405 signals fed to the sets on one side of the workshop.
I decided to get the ITT version out of the shed and have a look at it. The set came from a local auction place some time ago with another set that I wanted. I had briefly looked at it at the time and decided it was a bit scruffy, the back is melted in one corner and it was dead. Looking a bit scorched around the rectifier, the RGD was much better so the ITT was decreed as a parts set and put to one side in the shed.
I put it on the bench and gave it a bit of a wipe over, I had a look at the rectifier diodes the board is a bit scorched around them and they were loose in the panel. removing the panel revealed they were all devoid of solder. I checked the diodes and despite appearances they seem to be OK. I soldered them in and tried the set. Dead, not a peep. A quick check found the primary fuse under the black cover was open and also higher rated than it should be. Someone has been here before...
I replaced the fuse and removed the CRT base to protect the heaters just in case, They checked ok for continuity and I wanted to keep it that way. I now had 20v on the smoother but no LT supply. I checked the regulator Transistor which proclaimed it's innocence, so this leads me to the regulator control circuit. Time to get out the diagram which means a visit to my mate Mick tomorrow who has one in the RTS books.
I have one of those sets, can’t remember if it’s the RGD or ITT version, got mine off eBay years ago! Mine had a dead IC in the RF/IF stages (Motorola chip, can’t remember the number!). I do remember it runs hot, I checked with a laser thermometer and it said it was around 65-70*C on the top of the cabinet! And then you get a set like the Hitachi that barely gets Luke warm even on the hottest days of summer!
@lloyd Sn76650N according to the circuit, I think there may be a Motorola equivalent which will be an MC-something. Decca used the same type on the Gypsy range, they would go blank raster with shortwave radio breakthrough ISTR. Seems to be a more common failure on the Decca than the ITT but that may just be my findings...
I have borrowed a circuit diagram and had a quick look before lunch. There are no shorts as far as I can tell on the LT line or "HT1" as ITT call it. The regulator is not working though and fails to start when the start up resistor R14 is shorted out. Transistor T1 looked a bit stressed as if it had been hot but it tests Ok, looking at the PCB though it has certainly been warm! T3 also checks OK. The layout makes fault finding a little more difficult than it looks in the diagram.
I have run out of time today as I have errands to run this afternoon, the clueless poking around will have to be resumed later! Any suggestions gratefully received!
Scorchio!
Well I think I have proved the fault is in the regulator circuit rather than it being shut down by a short elsewhere but buggered if I can find out what! The annoying thing is it's a such a simple circuit. There was I time I would have had this done in no time! I may have to get a 8.2 V Zener and check it by substitution. Everything else tests ok. If I link the Emitter to the Collector of the Series regulator Transistor effectively bypassing the regulator circuit the set comes to life. The LT is a bit high but not massively, a couple of volts or so. I won't run it like this for long just to prove that the rest of the set is OK. There is hum on the picture causing rolling and poor line sync but (I think..) it proves there is nothing shutting the regulator down as I have Line and frame scan, sound, and the set tunes in. So nothing is short. There's not much to the regulator circuit so in the end I cold checked every part apart from the Zener which does test as a diode (not short or open circuit.) Someone has definitely been here before. I have had enough of it for today! 🤪
Did you know that you can use a reverse-connected B-E junction on a BC547 or similar 100mA transistor as an 8 volt zener? It'll be somewhere between 7 and 9 volts, well within range of the pot.
In that circuit, if the zener wasn't zenering or it was a normal diode, the regulator would be turned off.
@irob2345 I did not know that! Many thanks for the info. I have just got home from a trip out to fetch a telly....I have a few jobs to do today and tomorrow but hopefully I will get some time over the weekend to have a further look.
Rich
This set is turning into one that you want to pick up by the handle and see how far you can throw it! My first idea of keeping it in the shed for spares is looking like one of my better ideas....
Today I changed the Zener and switched on. The set came on and for 30 seconds I had a picture. Then it went off! No L.T across the smoother. Two bridge rectifier diodes had gone OC!? I couldn't find a short or reason for this so I assumed as they had been previously cooked, unsoldered and checked, resoldered and now the set was working, loaded. This must have been too much!
I removed the diodes,, two of them now had loose lead out wires and what looked like a blob of glue coming out but these two still read OK! It was the other two that had gone O/C.. I fitted a replacement bridge rectifier and tried again! The set came on and stayed on! I set the LT voltage and did battle with the tuning pots which were really intermittent.
Running the set again it gave a good picture, and stayed on tune. Then there was a bit of a straining nose from the line stage and the primary of the LOPT sparked, farted smoke, the width came in, jumped out, the picture went large and dim. I didn't dive for the power switch, I decided **** it! let it suffer! The mains transformer rattled a bit and the set died! Line output Transistor very hot! It is a good job it isn't Tuesday 'coz Tuesday is bin day!
The set will go back in the shed until my next trip to the tip. I think I'll have a look at the dead Thorn 1590 next... 🤪
the primary of the LOPT sparked, farted smoke, the width came in, jumped out, the picture went large and dim. I didn't dive for the power switch, I decided **** it! let it suffer! The mains transformer rattled a bit and the set died! Line output Transistor very hot! It is a good job it isn't Tuesday 'coz Tuesday is bin day!
That description, it did make me chuckle, sorry. However, I totally get the sentiment, I'm sure we all do, sometimes you just want to serve up pain and beat the crap out of some of these unruly objects. I swear some sets have a stinky FU attitude, like they're saying, "I'm not going to wake up, no matter how hard you try to make me".
I'm wondering how your ' Pee Pee PYE' is going to behave. Likewise, I think I'm in for trouble with my mouldy Teletext Sanyo.
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