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UK Vintage Radio Repair and Restoration Discussion Forum (https://www.vintage-radio.net/forum/index.php)
-   Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players (https://www.vintage-radio.net/forum/forumdisplay.php?f=35)
-   -   Elizabethan LZ-29 (https://www.vintage-radio.net/forum/showthread.php?t=156005)

Sideband 27th Apr 2019 7:22 am

Re: Rectifier
 
Quote:

Originally Posted by Dorian27 (Post 1140040)
Thanks all for your help but I think this is to much for me I will leave it unless I can get similar with not much to do to replace . I don't think I am capable of doing all that

Don't unerestimate yourself! There are only four connections to make.... the replacement will be marked:

- ~ ~ + (the position of these may vary but the symbols tell which is which).

From your clear photos....white connects to one ~, red connects to the other ~. Connect - to any convenient chassis tag. You should connect an additional resistor in series with the + tag as already stated so all that happens then is that the yellow lead connects to one end of the resistor and the other end of the resistor goes to the + tag. Job done!

As I asked previously, are you sure the rectifier is faulty?

Diabolical Artificer 27th Apr 2019 8:05 am

Re: Rectifier
 
"Thanks all for your help but I think this is to much for me" Please don't get discouraged, we were all begginer's once, and still learning as you see from some of the mistakes I made in this thread. If you order one of these - https://cpc.farnell.com/taiwan-semic...ge%20rectifier or one that Trevor recommended, we can guide you from there, but it really is a simple fix, made a bit confusing by your old BR having five terminals instead of the usual four on most BR's. This in light of whether the old one is dead.

Apologies for the mistakes, of coarse 400v PIV wouldn't be enough, was forgetting PIV rating was in P-P and I thought we were talking about a dropping resistor after the RC filter to drop any excess voltage caused by the different forward V of the old BR and new.

Andy.

Dorian27 27th Apr 2019 5:37 pm

Re: Rectifier
 
Thank you all .I have managed to find an identical rectifier with a near home it is a Westinghouse same apart from part no but he said it would work well I fitted it and my recorder fired up and sounded great for about fifteen mins then the big green mains dropper resistor started smoking so I turned it off. Would that rectifier cause that or is this another problem?

Anyone with any ideas please.

HamishBoxer 27th Apr 2019 5:44 pm

Re: Elizabethan LZ-29. Rectifier.
 
Sounds like another problem, but first check the rectifier in case it is short through being underrated.

Station X 27th Apr 2019 5:52 pm

Re: Elizabethan LZ-29. Rectifier.
 
I've checked the circuit and there is no mains dropper. Do you mean the smoothing resistor R28 500R? If this is overheating then a possible cause is the smoothing capacitor C22 being electrically leaky.

Wire wound resistors do get hot. Has the HT voltage dropped?

Personally I'd have fitted a new bridge rectifier whose performance I could be sure of.

'LIVEWIRE?' 27th Apr 2019 6:04 pm

Re: Elizabethan LZ-29. Rectifier.
 
I'd agree with Graham and HB. Fitting a N.O.S. contact cooled(or any other type ) rectifier is, IMHO, asking for trouble. As others have said, it's not difficult to fit a modern silicon bridge rectifier. The two wires from the transformer secondary go to the terminals marked either 'AC' or with the '~' symbol. The Negative terminal on the new rectifier (marked - ) goes to chassis, and the Positive (+ ) goes to the smoothing capacitor via a series resistor. The Smoothing Capacitor should be checked and, if necessary, replaced.

HamishBoxer 27th Apr 2019 6:43 pm

Re: Elizabethan LZ-29. Rectifier.
 
I would have said smoothing cap too, if it was not for the fact the rectifier is of unknown rating.

Dorian27 27th Apr 2019 6:58 pm

Re: Elizabethan LZ-29. Rectifier.
 
It a big wirewound resistor with three terminals first part is marked 200ohm and I think the other half is 1.5k I think we'll that's the half that's getting hot it smokes this item is below the selector swiches I mean rewind play stop FF and the cables go to each motor

Station X 27th Apr 2019 7:22 pm

Re: Elizabethan LZ-29. Rectifier.
 
The service sheet, which I assume you have, mentions a mains resistor being mounted on the underside of the tape deck. It's 10W 2000R for 200 -250V models and 400R on 110 to 125V versions. Has it perhaps been replaced?

ms660 27th Apr 2019 9:36 pm

Re: Elizabethan LZ-29. Rectifier.
 
I don't have an LZ29 schematic but the big resistor could be the shunt resistor that sets the torque of the LH motor (supply reel) If it is it will be in circuit across the LH motor when in play or record, that motor being connected in series with the RH motor (take up reel) The two motors being in series across the mains during playback/record, that's the usual arrangement for these types of 3 motor decks.

Lawrence.

Sideband 28th Apr 2019 9:28 am

Re: Elizabethan LZ-29. Rectifier.
 
No point guessing with replacements. 'It's the same apart from the part number'......well it's not the same then!! It may well have a lower rating that the original. Now you have a situation of not knowing if the replacement rectifier has caused the problem or if there was an underlying problem that caused the old rectifier to fail (like smoothing caps) or if it is an entirely new fault that would have happened anyway. Selenium rectifiers even if unused, will not be reliable now as has already been stated.

You need to positively identify the resistor that is overheating by checking against the circuit. We may then be in a position to advise further.

60 oldjohn 28th Apr 2019 9:41 am

Re: Rectifier
 
Quote:

Originally Posted by Dorian27 (Post 1140363)
fired up and sounded great for about fifteen mins then the big green mains dropper resistor started smoking so I turned it off.

Might it just be years of damp and dust burning off ? More measurement need to be taken to be sure.
I wonder if the motor bearings are stiff adding more stress to this resistor.
John.

TrevorG3VLF 28th Apr 2019 12:17 pm

Re: Elizabethan LZ-29. Rectifier.
 
A resistor is necessary when replacing a valve rectifier to get the right voltages and restrict the pulse current. I have never measured the difference between a new selenium rectifier and a diode. Is a resistor necessary?

Dorian27 28th Apr 2019 5:49 pm

Re: Elizabethan LZ-29. Rectifier.
 
2 Attachment(s)
This is the resistor that's getting hot I have taken pics of it it is split in to to pieces on one item I think .The rectifier I replaced the original with is part no H31N08B02 identical in size and shape to original and made by Westinghouse like the original part no EC1 U567 could any one tell me if it is ok to use instead of original or not would it make that resistor overheat or not as I tried the recorder to day it worked but I turned it off before it got hot

ms660 28th Apr 2019 6:08 pm

Re: Elizabethan LZ-29. Rectifier.
 
I wouldn't have thought that a malfunctioning rectifier would cause that large twin resistor to get hot, it looks like the shunt resistances for the spool motors, they will get reasonably hot in use, a stiff motor/reel table would make them hotter.

Lawrence.

Dorian27 28th Apr 2019 6:36 pm

Re: Elizabethan LZ-29. Rectifier.
 
I have striped all motors cleaned and oiled all bearings and they seem to run nicely

Sideband 28th Apr 2019 6:44 pm

Re: Elizabethan LZ-29. Rectifier.
 
There appears to be a disconnected wire near the resistor. Where is that from?

Also why was it necessary to change the rectifier in the first place?

ms660 28th Apr 2019 7:56 pm

Re: Elizabethan LZ-29. Rectifier.
 
Just for general info....The link below shows the basic motor and shunt resistor set up for a Collaro Studio tape deck:

https://www.americanradiohistory.com...rch=%22collaro motor%22

That broadly agrees with the motor circuit of the Elizabethan Major which also uses the Collaro Studio tape deck and also has a single shunt resistance.

The OP's tape recorder clearly has a dropper consisting of two resistances, as apparently the Martin Recordakit did:

https://www.radios-tv.co.uk/wp-conte...in-1-small.JPG

The two resistors have been mentioned before:

https://www.vintage-radio.net/forum/...ad.php?t=63711

Lawrence.

Dorian27 1st May 2019 4:54 pm

5 Attachment(s)
Hi can any one tell me this resistor is has 3 cables comming off it it is like 2resistors in one one end has 200 ohm on it and the other has 1.5k on it the problem is that is getting very hot if used longer than ten minutes it smokes I. Believe it for the motor I have cleaned and oiled all three motors and they sound and run good so I don't know what to do or how or what I need to replace it can any one give me any suggestions as I am a novice at this thanks

Can any advise me please this resistor is getting very hot that it smokes after about 10min running I have cleaned and oiled all motor bearings and they are running quietly and smoothly.if it needs replacing what do I need as it seems to be in two halves made to one on one side it has 200 ohm and the other 1.5k can you help please I uploaded pics

Sideband 1st May 2019 7:12 pm

Re: Elizabethan LZ-29. Rectifier.
 
These resistors are designed to run hot and if it's been handled, there will be grease from fingers and hands present. It will smoke and burn off as will any dust that is present. It may be OK....keep an eye on it for 20 minutes or so and the smoke should decrease as the grease burns off.

These resistors do run hot....in many cases far too hot to touch. That looks like it might be 15 or 20 watts. That is why they are big, wirewound and ceramic coated in clay. However if it starts to get red hot or the smoking doesn't stop .....there is a problem!

The resistor isn't smoking because it's faulty so no point in replacing it.


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