Hi guys so I'v now got the above stereo gram too! Just changed electro caps and a couple of others that iv so far been able to find. The stereo only had one original speaker a rola 8mx but listed as 2ohm. This is contrary to every other iv seen at 15ohms. Anyone know about this? Can I grab any 2ohm speakers to replace with/anyone have some recommendation? I also have noticed the transformer has melted a lot of wax doesn't seem to be now tho and it works what should I do? Thanks!!

G'day Monaro,

Good to see you are back. I am not sure where you would get 2Ω speakers but I'd be testing that transformer pretty quick. Whilst intermittent faults do not occur often in transformers you may have such a fault there. You'll need a megger to do it right and each winding will need to be tested.

Being a Kriesler, a replacement transformer should not be difficult to locate though there may be a short wait until something becomes available.

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

Yes I'm back - I forgot my username so couldn't log in!

Is testing a transformer pretty easy? I haven't done that before. The transformer doesn't seem to get too hot just warm and everything is working properly ( I have two old 8" 2ohm woofers from a car I stripped that I have connected for the moment - not much range though so doesn't sound great!).

Where do you think is best to look for a replacement?

Pretty new to this game and parts don't seem to be as readily available as I thought!

It may be okay and the receiver may have just had a hard life being stored in a very hot, dry place for a long time though I doubt it. In my experience power transformers seldom get any temperature in them under normal load unless the rectifier valve is placed nearby and heat is radiated across.

Resistance (continuity) tests on each winding plus an insulation test between each winding will be needed. When I do this I use the results from the meter to calculate the current flow - if the amps results seem too high I just replace the transformer. I have a few in the garage that have gone up in smoke, ending their lives fairly quickly. One day I will be lucky enough to set up a jig for rewinding them.

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

I doubt the wrong speaker would cause the power transformer to heat up.

Being Kriesler, doesn't it have a schematic stapled to the back?
What is the primary impedance of the audio output transformers, and do they have a model number?
Is it a pair of 6M5 valves for audio output?

The reason I ask is I'm about to have a stereo pair I could send you,
but it will be into next year before I can replace them.
I did have a pair of Hammonds to go in mine, but I just borrowed one for another radio.
Mine are for 15 Ohm speakers though, I'm replacing them to use new 8 Ohm speakers.

I'll bet the Kriesler's AM receiver is out of alignment too ;)

Thanks yes I'm pretty sure something is wrong too - the on off switch failed after only a few uses which could be due to too much current being drawn through it. Now this could have happened the couple of times prior to recapping it I don't know - apparently some failed caps can cause transformers to fail. Mind you I haven't replaced them all yet either....

I think i'm best off replacing transformer rather than taking chances - do you know how to get transformer specs? The transformer for this radio is 18-101 but they are obviously not all the same because my 11-97 has 18-4150.

The voltages are not printed just under the lugs on black paper?
You might have to remove some wax.

Thanks for all the help guys

I'll check the schematic on the rear of the stereo but I have an 11-77 schematic I got off kevin chant and it shows 7k/2ohm speaker transformers so there must have been a special rola speaker made up for it?

Yes there is a pair of 6M5's your spot on!

I will look at the mains trans again but from the schematic it provides 260v ac (with resistance of 82ohm?) to valve 6 (6v4) and 6.3v / 47ohm.

It depends what your objectives are.. restore to vintage or modernise it.
You will certainly be welcome to my pair of ROLA audio output transformers when I sort out a new Hammond... if you think you can track down a pair of 15 Ohm speakers.

Have a look in the "Special Projects" forum.
If your chassis is the same as mine, I will be able to take measurements you might need, since my chassis is still accessible.

Original:
Image Link

Thanks Art thats very helpful! I will let you know I think I need to sort out the power trans first and once I have that problem under control will hunt for speakers and if I find a good pair of 15ohm's which there seem to be many more of, I will contact you!

I want to restore it but I am also happy to make improvements too (I have an 11-97 and like the sound from it's magnaflux 12 inch 15 ohm speakers) so upgrading the 11-77 to these is an option with your output trans. Do you think the 6m5's will run them ok?

Just saw your pic your output trans look identical dimensions to my 11-77! Actually they are probably the same ones in my Kriesler 11-97 which are 10k/15ohm? They certainly put out some good power running 6 speakers in that - two 12inch, two 6 x 4 inch and two tweeters!

Nice unit.

The 11-77 was one of the first stereophonic radiograms made by Kriesler, dating from late 1958, but went on the market in 1959.
.
I did one of these up for a friend years ago, the only concern being a nice big fat sheet of asbestos underneath the lid to access the chassis. (Perhaps there was enough heat generated there to cause some wax to melt!)

The primary impeadance for the output transformers for the 11-77 is 7K. You could replace them with 7K/15ohm types, which are more common in later Kriesler grams.

To see if the power-transformer has survived its ordeal, try running it unloaded (that is taking all the valves and dial-lights out). Then check to see how warm it gets. If all ok, run it loaded with the valves & dial-lights back in, carefully monitoring the temperature. If the transformer becomes too hot or starts to smell then consider it faulty. If faulty, you should be able to replace it from a later Kriesler gram. For a replacement just make sure the HT voltages are the same and can handle the total filament current. The mounting footprints for Kriesler power transformers appear to be the same right through out the 1960's.

I'm no expert, but if the impedance is matched, I don't think it's a problem.
If you run three speakers per channel, you'd need to consider the total impedance each channel of course.

Let me know if there's any measurements I can take on my
power transformer.
I can't conduct proper tests, but if you work out they are identical,
a cheat should be possible.. measure output voltages, also measure DC resistance across windings... normally useless, but identical units should closely match.

Oh wow thanks for such valuable info And nice warning about the asbestos sheet I noticed there was the rectangle sheet of something under the chassis lid and didn't even think about what it was! I've done quite a bit of tinkering on the chassis but don't think i've disturbed that sheet (much!). Did you remove it or leave it there?

Glad to know I can swap the output trans as it would give me much more flexibility with speakers.

With the power amp, it gets warm to the touch but not hot with it running. How hot (if at all) should it get unloaded without valves? I haven't removed the valves at all is there any chance that by disturbing them I can damage them they should just pull out easily shouldn't they?

Thanks!