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-   -   Elizabethan LZ-29 (https://www.vintage-radio.net/forum/showthread.php?t=156005)

Dorian27 25th Apr 2019 5:30 pm

Elizabethan LZ-29
 
2 Attachment(s)
Can any one tell me where I could get one of these please it is a Westinghouse EC1 U567 thank you

Nuvistor 25th Apr 2019 5:57 pm

Re: Rectifier
 
Use a silicon bridge rectifier of a suitable rating with a series resistor to make the rectified output voltage correct.
A selection at this web site but many other suppliers.

https://uk.rs-online.com/web/c/semic...ge-rectifiers/

Dorian27 25th Apr 2019 6:14 pm

Re: Rectifier
 
Not sure how to do this but thanks

Sideband 25th Apr 2019 6:30 pm

Re: Rectifier
 
Well there is no point in trying to find a NOS (New Old Stock) Westinghouse rec as it will be past its best and won't be reliable. I'm sure we can help you wire in a suitable silicon bridge rectifier if we have more information on the item you are restoring/repairing. It's not difficult...just requires care to get the four connections correct. So some good pictures of what you have and the model number of the item and we can then give practical advice on a suitable silicon rec replacement and how to go about wiring it in place of the Westinghouse.

The connections are clearly marked on the original and similar markings will be shown on the replacement....so it should be dead easy!

60 oldjohn 25th Apr 2019 6:30 pm

Re: Rectifier
 
What is it out of? Please don't be tempted to buy a "good" second hand one, it will not last very long.


John. Crossed with Sideband.

Dorian27 25th Apr 2019 10:42 pm

Re: Rectifier
 
Hy thanks all for your help the rectifier is out of ELIZABETHAN LZ-29

Dorian27 25th Apr 2019 11:22 pm

Re: Rectifier
 
2 Attachment(s)
Here are pictures I took before dissmantlin the rectifier The pictures after dissmantlin are further up on another thread hope they help thanks

60 oldjohn 25th Apr 2019 11:27 pm

Re: Rectifier
 
Have you got the circuit? if not its available top right of this page for 1.99. The rectifier should be bolted to the chassis, it acts as a heat sink. Where the circuit points to 270 near MR1 that wire need cutting and a resistor inserting, maybe 200 ohms 5W also bolted to the chassis to dissipate the heat. Exact value not critical but should be chosen to get near the 270V indicated. Once you have that sorted consider changing MR2 in the magic eye circuit an ordinary Silicon Diode, the 100k resistor may need increasing.


John.

Diabolical Artificer 26th Apr 2019 7:07 am

Re: Rectifier
 
Replace Bridge Rectifier as suggested above, any 400v 1A or above rated Bridge Rectifier will do or nick one out of a PC ATX PSU but check the datasheet first, the Bridge Rectifier's datasheet that is.

After the Bridge Rectifier between HT and + of the BR pop a big 5W low value resistor from your parts stash, 200 - 270r as suggested above or to start use a 100r. Clip your voltmeter leads either side of the resistor and switch the set on briefly but long enough for it to warm up. Divide the voltage reading by the resistor value to get the I or current, it should be around 100mA or below broadly speaking. From the schematic find out what HT should be then divide this figure by I (current) to get what value R you need, no need to get bang on as long as it's +/- 10v or so it'll be right.

Fit new R and then check HT is on spec. One other thing the schematic value will probably have been measured with an Avo or similar, so HT as measured with a DMM will be higher. Not sure if there is a rule of thumb to help figure the HT value as measured by a DMM, add 20v perhaps? Others here will know.

Andy.

Station X 26th Apr 2019 9:23 am

Re: Rectifier
 
1 Attachment(s)
Extract from circuit attached.

TrevorG3VLF 26th Apr 2019 11:03 am

Re: Rectifier
 
Andy #9
The resistor voltage drop will be higher than what Mr Ohm would say because the current comes in pulses. The resistor dissipation would also be higher than that calculated from a steady current.

The meter voltage error will depend on the meter resistance and the source resistance. I would think that there would be very little error when measuring the HT voltage with a low source resistance.
Some cheap digital meters have an input resistance of 1M which is the lower than an analog meter 20k/V on the 1kV range. Posher digital meters have an input resistance of 10M. The error can be calculated if you are so inclined.

Nuvistor 26th Apr 2019 11:52 am

Re: Rectifier
 
Would a 400 PRRV be good enough? I would have gone for one at least twice that rating, the price is little different for a 1000v one and they are similar in size.

ms660 26th Apr 2019 12:08 pm

Re: Rectifier
 
Out of interest:

https://www.kevinchant.com/uploads/7...placements.pdf

Lawrence.

Orakle42 26th Apr 2019 1:50 pm

Re: Rectifier
 
Am I missing something here? If you are replacing one semiconductor bridge with another why should any new series resistor need to be added?.
If the original component was selenium it might be necessary as the Vf would be higher but replacing a germanium with silicon would make very little difference. The original appears to have the connections marked so replacement with one of any number of devices should be quite straightforward. Unless "authenticity" is the objective I would have thought that any 1000v piv 2amp bridge would suffice and provide more than adequate safety margins. (I am guessing about a suitable current rating being unfamiliar with demands of the actual circuit). The circuit shown appears to have a 270v HT after the bridge, this would seem to indicate an rms input voltage from the transformer of approximately 195v. The minimum piv rating for the bridge should therefore be 550 volts. (All figures are approximate)

Orakle42.

Nuvistor 26th Apr 2019 6:33 pm

Re: Rectifier
 
I believe the original component is selenium, what makes you think it is germanium?

Dorian27 26th Apr 2019 6:41 pm

Re: Rectifier
 
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 I am an amiture at this and don't want to make things worse.i thought I could get a straight equivalent replacement.

Nuvistor 26th Apr 2019 6:44 pm

Re: Rectifier
 
There may be someone nearby who can show you if you ask around. It’s a very simple change but appreciate it seems much more if you have not repaired this type of item before.

Sideband 26th Apr 2019 9:07 pm

Re: Rectifier
 
Quote:

Originally Posted by Dorian27 (Post 1140040)
i thought I could get a straight equivalent replacement.

These rectifiers haven't been available for 50 years. What makes you think the existing rectifier is faulty anyway? Is the voltage output low? Is it just a guess?

TrevorG3VLF 26th Apr 2019 10:14 pm

Re: Rectifier
 
My very limited experience has been that selenium rectifiers go high forward resistance but would be OK in the reverse direction.
You could try to leave the existing bridge in place and connect a W08 (1.5A 800V) bridge across it. W08 Bowood electronics 30p. If things get hot, then remove the selenium rectifier and make a tag strip for the W08.
You could open the can and put four 1N4007 or UF4007 diodes inside. (1A 1kV)

G8UWM-MildMartin 27th Apr 2019 2:02 am

Re: Rectifier
 
Looking at the circuit, it doesn't actually make any difference which terminal the recommended additional resistor goes in series with.
The original has 5 terminals, marked with symbols, two of which (both -) are linked with a wire, so are effectively both the same, and everything connected to them goes to the (-) of the new one (via the resistor if you choose not to put it in series with one of the other legs). A replacement has 4 terminals, marked with the same symbols.

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.

Boater Sam 1st May 2019 7:50 pm

Re: Elezebethan LZ29 resistor
 
Do you have the service sheet?
This is described as the mains resistor but doesn't appear on the circuit diagram on the ERT sheet.
It is supposed to be a 2K ohm 10 watt resistor in total for a 240v machine. Is it in series with the motors or the amp transformer or even both?
It will run hot, but how hot is it?
Smoke could be just dust or damp burning off. If its hot, it does NOT need replacing.
What works on the deck? Does the amp work?

GrimJosef 1st May 2019 9:32 pm

Re: Resistor
 
Looking at it I think it may be meant to get very hot. It's of a type (wirewound) which is often used to dissipate relatively high powers. Apart from the temperature, do you have any other reason to believe that there's a problem with it ?

Cheers,

GJ

Station X 1st May 2019 9:54 pm

Re: Rectifier
 
Quote:

Originally Posted by Dorian27 (Post 1140363)
then the big green mains dropper resistor started smoking so I turned it off.

Measure the AC voltage across the resistor section or sections that is/are getting hot. Square the voltage and divide it by the value of the resistor. The result is the amount of power the resistor is dissipating.

Dorian27 1st May 2019 10:10 pm

Re: Elizabethan LZ-29
 
Yes the amp works fine. I have cleaned all motors and oiled bearings with a ligh oil and all runs nicely no noisy motors and play at correct speed also FF Rew good just I am worried because I get smoke off that resistor

Dorian27 1st May 2019 11:06 pm

Re: Elizabethan LZ-29
 
2 Attachment(s)
I will try to upload pics of it ok might help

Boater Sam 2nd May 2019 9:41 am

Re: Rectifier
 
Quote:

Originally Posted by Station X (Post 1141738)
Quote:

Originally Posted by Dorian27 (Post 1140363)
then the big green mains dropper resistor started smoking so I turned it off.

Measure the AC voltage across the resistor section or sections that is/are getting hot. Square the voltage and divide it by the value of the resistor. The result is the amount of power the resistor is dissipating.

Have you done this yet? It will answer your problem.

A risk of repeating everybody, IT IS MEANT TO RUN HOT.

You have oiled the motors and mechanism, one drop of oil or an oily finger on this resistor will make it smoke for a surprisingly long time.

Dorian27 2nd May 2019 12:34 pm

Re: Elizabethan LZ-29
 
Not sure how to measure voltage where to put meter leads as I am a novice at this also it was smoking before I oiled motor bearings once it starts to smoke I turn it off don't want to blow anything else or will it be ok to leave it running

Station X 2nd May 2019 1:22 pm

Re: Elizabethan LZ-29
 
1 Attachment(s)
Connecting a meter "across" a component means connecting the meter to the tags or leads at each end of that component.

Start by setting the meter to the highest AC voltage range then switch down the ranges until you get a sensible reading.

Dorian27 2nd May 2019 1:25 pm

Re: Elizabethan LZ-29
 
Ok will connect meter tonight or tomorrow I take it set to AC 250V or higher

Dorian27 2nd May 2019 1:26 pm

Re: Elizabethan LZ-29
 
Sorry just seen your post to set to highest sorry


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