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 Modified Tasma 1001
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 Return to top of page · Post #: 1 · Written at 1:13:14 PM on 3 August 2016.
RobEddy's Gravatar
 Location: Adelaide, SA
 Member since 31 May 2016
 Member #: 1933
 Postcount: 3

Hi everyone.
Need some assistance with a Tasma 1001 which I am "restoring". Given to me by a family member to restore - its history is unknown except that it has some sentimental value. Upon disassembly the following was at once apparent: 1. all the electrolytic and ceramic capacitors have been replaced. 2. the valves with the exception of the rectifier valve have been replaced with Miniwatt valves which has included the installation of a replacement valve base presumably to accommodate the different pin configuration size. So this radio has been the subject of an extensive repair/ modification previously. Appears that this was done about 20 - 30 years ago - though a bit hard to tell.

This valve modification is somewhat disappointing as appears that the radio is now far from original. Given the sentimental value the radio, I would still like to get the radio operational if possible. I haven't traced the circuit in detail yet to further assess the extent of modification to accommodate these replacement valves.

So my questions are:
1. is/ was this type of modification common in the past to presumably address the availability (or lack of) the original valves or am I in possession of a sad case?
2. the valves currently installed are: 6AN7A (was 6A8G), 6N8 (was EBF2), 6BM8 (was EL3NG), and the 5Y3G rectifier valve which has its original base still installed. Are these replacement valves simply replacements (equivalents) of the originals except for the valve base size - am I that lucky?
3. are the original valves and bases still available/ acquirable?

A couple of photographs below.

Thanks in advance
RobEddy
VK5RY

Tasma 1001 Mantel Radio
Tasma 1001 Mantel Radio
Tasma 1001 Mantel Radio


 
 Return to top of page · Post #: 2 · Written at 2:31:57 PM on 3 August 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1381

Eww.

Replacing valves in that fashion destroys whatever historical or collectable value it might have had.

6A8G is a very old mixer type, the 6AN7A has superior performance.

EBF2 and 6N8 both have a remote pentode and 2 diodes, the 6N8 having slightly more gain, but in practice should be much the same.

EL3NG is a large and hot output pentode. The 6BM8 has an additional triode inbuilt. If it was wired up then the radio will have more volume than it did before.

The output impedence will be different (8000 vs 7000), but it wouldn't make that much difference.

Question 1 is speculation... who can say what the reason was? The 6A8G and EL3NG have a number of plug-in replacements, and the EBF2G could be replaced by EBF35.


 
 Return to top of page · Post #: 3 · Written at 3:06:16 PM on 3 August 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6014

Original line-up for that 1946/47 model was: 5Y3G, 6A8G/EK2, EBF2, EL3NG.

Who knows who made the mods and why. It could have been a case of using what was available, or an attempt to improve performance. Back in the day these were simply household appliances and the order may have been "just fix it!".

This model appears fairly frequently at HRSA auctions, usually covered in paint spatter and the case is often cracked at the top due to people carrying it by placing a hand under the top. Those can be got for not many dollars.

If you're keen to have an original set, and your case and dial are in good condition, then you might keep and eye out for a chassis donor.


 
 Return to top of page · Post #: 4 · Written at 6:38:44 PM on 3 August 2016.
Garyoz's avatar
 Location: Perth, WA
 Member since 19 November 2008
 Member #: 381
 Postcount: 239

I completely restored my Tasma 1005 awhile ago and that included replacing all valve sockets. The 1005 is very similar to the 1001.
See:-

https://vintage-radio.com.au/default.asp?f=1&th=651&offset=2

You should be able to do the same as I think the Local Oscillator, IF's and mains transformer will be the same.

Also Kev has the circuit for the 1001:-

http://www.kevinchant.com/uploads/7/1/0/8/7108231/aus_tasma_1001_sch1.pdf


 
 Return to top of page · Post #: 5 · Written at 9:33:43 AM on 4 August 2016.
RobEddy's Gravatar
 Location: Adelaide, SA
 Member since 31 May 2016
 Member #: 1933
 Postcount: 3

Thanks for the responses.
The radio case, dial etc are in very good condition As I said the radio has family sentimental value so I will get it working again in its current state. The family member (cousin) who owns this is not a radio collector or restorer so the value to him and his wife is contained in the radio - they would not be too concerned about its historic integrity.

Thanks Robbbert for the valve summary - it appears that I can keep the current valve configuration as is and get this set working. I will power up today (in stages) and see what happens.

Garyoz - very nice job - case and wiring immaculate. Wiring is probably better than when it came from the factory.

GTC - good suggestion. I will keep an eye out for a replacement chassis and swap over. It would be nice to see it right.

Thanks again - your help is appreciated.

Rob
VK5RY


 
 Return to top of page · Post #: 6 · Written at 5:54:34 PM on 4 August 2016.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1133

If you want to get the Tasma working again in its current state & keep the circuit original you could consider using these valves:

6BA7 (6A8G), 6N8 (EBF2) & 6M5 or 6BQ5/EL84 (EL3NG). Some wiring changes to the existing 9 pin sockets will be required.


 
 Return to top of page · Post #: 7 · Written at 8:38:59 PM on 5 August 2016.
RobEddy's Gravatar
 Location: Adelaide, SA
 Member since 31 May 2016
 Member #: 1933
 Postcount: 3

Powered up the radio today after replacing a couple remaining electrolytic capacitors. Was lucky the set worked pretty well straight away. A bit of a tune and it sounds quite good. The tone control doesn't seem to have any effect (will investigate but appears wired correctly and switch is OK). The bakelite case and knobs cleaned up well and the glass dial is in good condition - the case actually polished up really well so it looks great. To complete needs some speaker cloth and a cotton power cord.
So given its history, its internal modification and the home to which it is destined I'll consider the restoration (more a clean up) complete. I'm sure my cousin will be pleased and the radio will take pride of place somewhere in his home.

Thanks for the help and suggestions.
Rob VK5RY


 
 Return to top of page · Post #: 8 · Written at 8:43:11 PM on 5 August 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6014

The mods would affect its resale value, but a happy owner with a working radio is probably the best outcome given the circumstances.


 
 Return to top of page · Post #: 9 · Written at 9:18:15 PM on 5 August 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1381

That 5Y3 would be the most modern-looking one I've ever seen.

Pity we didn't get to see the underside.

Agree with GTC - since it isn't for a collector, who cares what's inside, it just has to work.

Seems like a good outcome in the end. Smile


 
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