2.5Ω Transformers - 30-A, 510- & 610-ST

[TheRed1]

Among the many new Fisher console manuals Jon has recently uploaded to the Fisher Consoles website are the 1960 Custom Electra III (model 440) and the 1959 Stereo Companion (model 560). This new information finally sheds some light one of Fisher's quirks: the 2.5Ω ONLY transformers found on some 30-A amps and seemingly all of the 610-ST (and 510-ST) chassis.

***A big 'Thank You' to Jon (aka: Jonboy55) for all the work he has put into making both service and owner's manuals for Fisher consoles available.***

Below is the speaker schematic for the Custom Electra III:

It shows 3 presumably 8Ω speakers connected in parallel which would have an impedance of approximately 2.5Ω. It even states that both L & R speakers are identical. What continues to baffle me is that the 30-A's that comprise the B channel in all the CE IIIs I have seen have all been of the 30,000 series with the 4, 8 & 16Ω taps. I guess the 4Ω taps would be close enough. It's just odd that that Fisher didn't use the 10,000 series 30-As which were almost an exact match for the amp in the 510- and 610-ST's

Here are the three different series of 30-A's used in the model 560 Stereo Companion:

10,000 Series 30-A

20,000 Series 30-A

30,000 Series 30-A

Below is the amp section of the 610-ST for comparison. Note the similarities to the 10,000 series 30-A's. There are only two minor cap value differences: C61 (which is C2 on the 30-A) on the the 610 is 150µµƒ, 500V but 100 µµƒ, 1000V on the 30-A, and C62 (which is C5 on the 30-A) on the 610 is 24 µµƒ, 500V but 150 µµƒ, 500V on the 30-A.

Another odd thing I have noticed is that Fisher's serial numbers appear not to have been issued entirely chronologically. The 30-A in my 1959 560 has a higher number than the 30-A in my Sister-in-law's 1960 CE III.

I opened up the speaker compartment of my 560 for the first time today to see how its speakers were connected. I had previously thought that it had 3 identical 8" speakers. Now I see that the bottom one has a larger magnet and a different part number. Would that be the woofer? These are wired in parallel, too, but without any sort of crossover circuitry - not even a filter cap like the one on the CE III's tweeter.

 

[audiodon]

Ah this is a great thread I'll be printing out for future reference. I've run into this a few times. Speakers in parallel without a crossover = lower impedance. Makes too much sense.

 

[visman]

TheRed1 - thank you and excellent information.

I'm traveling this week but when I get back I'll check out my 560 Companion which has the 4,8 and 16 ohm connections on the 30A. I am almost positive mine was connected to the 8 ohm terminals - so it will be interesting to see what the speaker config. is. I'll also get the serial number information for the records.

 

[rwj0j0]

i noticed that my CEIII has 2.5 out off the tuner and 4.0 off the 30a.
haven't had the chance to dive in to far yet though. I have looked at the speakers but not in any great detail. I really think there is a more complicated crossover in mine. Its more than one capacitor per channel for sure.

 

[TheRed1]

I am almost positive mine was connected to the 8 ohm terminals - so it will be interesting to see what the speaker config. is. I'll also get the serial number information for the records.

You posted a photo of that, didn't you? I remember making a mental note of that since my 560's speakers weren't connected when I got it. Now I'm starting to think the 4 ohm taps might be the correct connection. Even if the speakers were each 16 ohms connected in parallel their impedance would still be closer to 4 ohms than 8.

Since your 30-A has the 4, 8, and 16 ohm taps, I'm going to guess it's from the 30,000 series. Another irregularity I have noticed is that both my '59 and rwj0j0's '60 30-As actually have serial numbers in the 300,000 series followed by a letter. I'm thinking they're really in the 30,000 series but for some reason they have an extra number at the end which may signify something. Does anyone have a guess what the letter at the end of the serial number signifies?

I really think there is a more complicated crossover in mine. Its more than one capacitor per channel for sure.

It might be like my 1959 Contemporary II which uses two caps wired in parallel but which might well have been shown on a schematic as a single cap.

 

[larryderouin]

I'm beginning to think that FISHER used a Alpha designator at the end of the serial for multiple year models. I'm seeing that on my S.S. FISHER units also.

A for the 1st year, B for 2nd, etc.

 

[TheRed1]

I went back and dug up visman's original post to see if I my recollection of what speaker taps were connected was accurate. Nope, it was 16 ohms. However, that might make sense since it looks like his speakers are wired in series. I see from the speaker date codes that his 560 might be an earlier version dating from 1958. It's hard to tell for sure since the bottom speaker didn't make it all the way into the frame but it looks like all the speakers are the same.

Larry, are you suggesting that all Fisher components produced during a given year would have the same letter code, OR within the production of a specific chassis (the 30-A for instance) the letters would indicate which year of production - starting with A? My '59 30-A ends in 'F' and my Sister-in-law's '60 30-A ends in 'H'. I suppose F could be '58 and H '60 but I don't think the 30-A dates back to 1953. I'll check my other Fisher chassis:

TA-500 = NONE
TA-600 = B
510-ST = B
610-ST = F
R-30-S = B
400 = J

I wonder if they could be the MONTH of production. Anyone have a letter beyond L?

 

[rwj0j0]

1 5uf cap? I think not!

 

[visman]

TheRed1, you are correct (and wow what a memory).

Here is the original shot of the 30A as received in the 560 and it is connected at 16 ohms.

I'll get some speaker shots this weekend.

 

[larryderouin]

Larry, are you suggesting that all Fisher components produced during a given year would have the same letter code, OR within the production of a specific chassis (the 30-A for instance) the letters would indicate which year of production - starting with A? My '59 30-A ends in 'F' and my Sister-in-law's '60 30-A ends in 'H'. I suppose F could be '58 and H '60 but I don't think the 30-A dates back to 1953. I'll check my other Fisher chassis:

TA-500 = NONE
TA-600 = B
510-ST = B
610-ST = F
R-30-S = B
400 = J

I wonder if they could be the MONTH of production. Anyone have a letter beyond L?

It is a distinct possibility. However it could be a month too as you pointed out.

 

[TheRed1]

TheRed1, you are correct (and wow what a memory).

No memory involved - not much left anyway. I created this post in the Fisher Consoles sticky (and there's a link to it in post #1) so that I - or anyone else - can easily locate the old Fisher console posts:

http://www.audiokarma.org/forums/showthread.php?p=4490618#post4490618

It's overdue for an update with some of the new Fisher consoles that have surfaced recently, like rwj0j0's CE III. I'm camping this weekend but I'll try to make that a priority.

1 5uf cap? I think not!

Holy smokes! That is quite a bit different than the schematic. I see by the Jensen code on the speaker in your CE III (220932) that the speaker itself was manufactured in mid 1959. While not definitive, that may indicate that your Electra was an early production example. I went back and looked at the front page of the CE III schematic on Jon's 'Fisher Consoles' website and noted that it was for what was possibly the 2nd generation CE III - serial nos. 20,001 to 29,999 inclusive. That might explain the differences.

Any chance you could draw a schematic of your crossover network?

 

[MickeySmile]

Hi all,
I have the Fisher 510-ST amp with 2.5 ohms transformer. I want to replace it with another transformer that using for 30-A. Is it OK just swap the transformer?
Also anyone has the schematic for 510-ST, could you upload it. I would like to restore my 510-ST to use it with the 30-A. Thanking in advance for your help!

Binh

 

[jonboy55]

Here is the link for a 510 Service Manual:

http://www.fisherconsoles.com/consolette 510 service manual page.html

 

[MickeySmile]

Here is the link for a 510 Service Manual:

http://www.fisherconsoles.com/consolette 510 service manual page.html

Thanks Jon! :thmbsp:

Binh

 

[jaymanaa]

Thanks Red1, I appreciate it.:thmbsp:

 

[chinacave]

Wow -

Thanks The Red1 -

I have (until now) never been able to find a schematic for the sub-30001 ser # 30-A's - and here we have a comparative parts list as well!

Much appreciated!

 

[larryderouin]

I discovered in opening up the my ST510(Red's old one) and the 560 companion(Buglegirls old one) that the speakers are all 8oHm, 2 with a whizzer cone and one without. That would account for the different part numbers. All Jensens. Found that the speakers that were in my oldmotorola (SK-47) are identical to the Jensen's in the FISHER's. On both cainets they are all in parallel to give the amp a 2.5oHm load. my 510 has the 2.5 oHm opt and the 560 the 4-8-16 setup. I set the 560 to 4 oHm.

 

[larryderouin]

Comparing the 510-610-560 schematics and parts lists, the 2.5oHm output transformers are all the same #. If you are inclined to go with a 4-8-16 oHm output transformer in the 510 or 610 or Custom electra III you could use the 4-8-16oHm transformer out of a scrap 30A. Should be a straight wire in. Then make the cap and resistor changes per the 30A schematic if needed. Or get Heyboer to make a new transformer.

Larry