4th May 2020, 10:57 am | #121 | ||
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
Last edited by audion_1908; 4th May 2020 at 11:04 am. |
||
4th May 2020, 12:29 pm | #122 | |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
Hi. When I get a chance I'll try to take some inductance measurements on my AM radio IFTs. They are mostly interchangeable from other make sets changing like for like obviously. I did however read that there can be a variation in the phasing of the windings ie the start/finish of one winding in relation to another. Installing the wrong type will certainly not work from what I gather. I think it was ex forum member Argus25 that pointed this out a little while back. Re your IFTs. If I was to refit the IFT that you've tested then I'd want to confirm that the ceramic cap is in order first. It looks a bit fiddly to see with the wax. A good test would be check that the IFT will resonate at the radio's correct IF. I can't recall where I saw this demonstrated but there was a simple test bed circuit in one of the magazines. You'd use an RF signal generator and oscilloscope. If you have a wobbulator (sweep generator) it would be a good way to check the response curve of the IFT. Regards, Symon |
|
4th May 2020, 12:54 pm | #123 | ||
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
in the test circuit. Like this ? From http://theradioboard.com/rb/viewtopic.php?t=7750 Identifying and testing unknown IF transformers? Is 390ohms right on the base? I probably have all the parts Last edited by audion_1908; 4th May 2020 at 1:11 pm. |
||
4th May 2020, 1:15 pm | #124 |
Banned
Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
|
Re: Wet 1969 ITT-KB junior battery radio
When you say the 'scope needs recapping, does it function at all? I tend to not worry so much about the accuracy of my old Philips 'scope but just the ability to display a trace & show if something's oscillating or not. For the purposes of this test I'd expect an uncalibrated/inaccurate 'scope to be just as useful.
(Same story with my sig gen, suspect a weak valve so it works around 150-900Kc/s but anything outside those ranges it dies! It's supposed to go up to something like 180Mc/s!) It's good that the IFT's appear to have been filled with goop as it should have preserved them, I'd agree with leaving the rest in place on an "innocent until proven guilty" basis. If that cap across the base has died, I'd bet Shango's Silver-Mica disease repair method of leaving the core roughly where it started & adding a trimmer cap and tuning that to find the value would work. (or just throw 100pF across it if you're feeling the Jason JJ Cruz vibe). |
4th May 2020, 1:53 pm | #125 | |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
If I have the IF transformers open I can cut the wires to the capacitor in the base of needed and use an external cap like you sed, but I want to test it first, also I have no Silver-Mica caps. I will attempt to build the ift test circuit with what I have, where is best to connect the oscilloscope? Last edited by audion_1908; 4th May 2020 at 2:10 pm. |
|
4th May 2020, 2:09 pm | #126 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
I found the kit box for the universal component tester, it looks much better now, and I am less likely to brake it. |
4th May 2020, 7:22 pm | #127 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
|
Re: Wet 1969 ITT-KB junior battery radio
Hi.
Re. the pic in post #123 that's a BFO type circuit and was not what I'd seen before for testing IFTs and I am not sure how this can be used. I believe it can be used in conjunction with another AM radio using the same IF and peaking the test IFT for heterodyning. Maybe another forum member can explain how that circuit can be used in practice for the TOKO IFTs and regarding coupling etc. I think one way to test the IFT is to apply the correct IF (say 455kHz) from a signal generator and look at the sinewave on the 'scope and peak the ferrite screw for maximum amplitude. Again, if any other forum member with more experience, particularly with the TOKO IFTs, can share their method of testing it would be great to see their aproach. All my testing of IFTs has mainly been setting them up in circuit by peaking their response at the required IF by using the standard setup of RF signal generator and output meter across the loudspeaker. I sometimes bring out the wobbulator and 'scope but it's a more involved process. Regards, Symon |
4th May 2020, 7:32 pm | #128 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
|
Re: Wet 1969 ITT-KB junior battery radio
I can't see what the problem is. Just give it a wipe with a damp cloth and realign it. Done!
I found an HMV 1807 television chassis buried in a garden at Crawley. Some of the components had literally dissolved and all the pins on the tube were rusting away. J. |
4th May 2020, 7:52 pm | #129 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
|
Re: Wet 1969 ITT-KB junior battery radio
Hi
Talking about corrosion and valve pins in particular, you sometimes come across valves with really bad green corrosion on the pins and wondered there must be something more than just damp that's caused it. I think I read that in some Kradlepak boxes that Mullard used this could be a problem. I tried an experiment, back in 2010 by putting a faulty 6F22 valve from my GEC BT322 out in the garden where if was well exposed to the elements but not in a place where it would get broken. The idea being to find out how the pins will cope. I retrieved it a few months ago after 10 years out in the open. I was amazed to find the pins corrosion free. How can that be so? Regards, Symon |
4th May 2020, 7:58 pm | #130 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
|
Re: Wet 1969 ITT-KB junior battery radio
|
4th May 2020, 8:00 pm | #131 | |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
|
|
4th May 2020, 8:02 pm | #132 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
It's been scrubbed in a sink! As I thought water can't do any more damage!
|
4th May 2020, 9:00 pm | #133 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,819
|
Re: Wet 1969 ITT-KB junior battery radio
I've been restoring an Ekco A22 since last may, and that was a rusted heap! It's still not as bad as your radio though! A22 restoration thread
I've had a go at some pretty rusted up speakers before, even made them work well again! But I think I'll pass on your one, I think it would be best to lay it to rest somewhere nice! Regards, Lloyd. |
4th May 2020, 9:19 pm | #134 | |
Banned
Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
Agree I'd like to see the thread on that garden telly if there is one! On the 'scope, I hadn't realised it was that age to have paper caps. Of course wouldn't suggest powering up anything I cared about with those in place! My PM3200X is just new enough to be fully transistorised (which was fun repairing as could only find the schematic for the ECC83 version, and even then only in Dutch! Got there in the end though!) Oh and Lloyd I think perhaps someone had attempted to lay that 'speaker to rest some decades ago, along with the radio it was contained in, only for it to be exhumed by an Ebayer. God alone knows what'd happen if the remnants of the unusable parts from this resurrection are dug up yet again sometime around 2065... |
|
5th May 2020, 12:18 am | #135 | ||
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
One thing I will do to the radio and scope when done is glue in a schematic, and maybe folding in a full service manual, to help the next person in there. Dose any one think I should start a thread on the Griffin scope? 2065 that's only 45 years 2089 is more like it 51 years, I hope it doesn't get buried again Last edited by audion_1908; 5th May 2020 at 12:25 am. |
||
5th May 2020, 12:39 am | #136 |
Banned
Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
|
Re: Wet 1969 ITT-KB junior battery radio
It'd be interesting to see a thread on the 'scope yes, if it has Sprague caps could it be American or perhaps taken to the US at some point in it's life? (Just pondering on the 120v/240v conundrum, if it is set up for 120v and someone tried a power-up over here it might account for the burned resistors :/ )
Is it a valve or transistor model (or hybrid)? |
5th May 2020, 12:57 am | #137 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
The scope is not American, apparently it was made by a company called scopex but rebranded Griffin, for use in uk schools and colleges, and uses a weird transformer hookup, it has no blown fuses, a 3amp in the plug and 1amp glass in the scope
my new cheap soldering iron tip is total rubbish, I will try filing it down tomorrow, as it's useless Last edited by audion_1908; 5th May 2020 at 1:17 am. |
5th May 2020, 1:11 am | #138 | |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
Before, the scrap pcb Bfo circuit, used nealy all recycle components only the 2n2222 transistor and the solder where new, I even pulled off the terminals off a dead 9-volt battery to make the 9 volt socket, it did prove to me it's not the 51 year old radios solder that's the problem but my soldering iron tip, I have a new one in the post and will try filing the old one down tomorrow I even reused 2 of the PCBs original components without moving them, I have found I should not have trusted 10+ year old 2 part epoxy I got in a £1 shop, it seems to have stalled while curing, and has the consistency of toffee hopefully sitting on a shelf overnight will improve it, any tips to try and harden it? |
|
5th May 2020, 1:23 am | #139 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,553
|
Re: Wet 1969 ITT-KB junior battery radio
That looks like a single transistor oscillator.
You just connect up the IFT and set the gain with a small preset pot in the emitter of the transistor until you get a clean sine wave on a scope. A frequency counter should read the IF frequency. |
5th May 2020, 12:46 pm | #140 | |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
|
Re: Wet 1969 ITT-KB junior battery radio
Quote:
Hi. I have done a few L and R checks for a TOKO 10T1 4603 IF transformer removed from my ITT Junior 21 see attached pic for details. Incidentally, does your screening can still have any legible markings left on it? I'll try to do some checks with the RF signal generator and 'scope later when I have the time. I'll also try out that BFO circuit and see if it will work in practice. These tests are going to be more meaningful than static L and R checks. Regards, Symon |
|