500B Problem/Question

walyfd

Well-Known Member
Hi, everyone. New poster here with a 500B question.

This 500B was given to me by a very good friend. I recently had it gone over by a professional shop. All the original Fisher tubes tested fine and the unit was recapped, etc. About a week after I got it home, the volume pot decided to croak which I replaced with a new one from Mark Oppat. (EXCELLENT to do business with BTW). While I was waiting for that, I completed the rebuild on a Garrard Type A with a Stanton 500 cartridge I plan to use as the record changer with the Fisher. May as well keep it vintage.

Here is the issue: the radio is SO loud, there is no way for the phono input to be adjusted to match the radio. On "1", the radio is loud enough for me, however, switching to any other function, it has to be turned to "1.5" or "2". I also tried an amplified turntable on the AUX ports with the non-amplified Garrard through the PHONO ports and played 2 copies of the same record simultaneously, switching from AUX to PHONO. Both sounded fairly equal. Passing through the radio stage, I tought the speakers were going to jump off the floor.

Is this normal? Any idea what it could be?

Thanks for any help!
 
There is probably nothing wrong -- especially if the symptoms are the same in both channels, and the FM stereo is working well. FM is a much louder medium today than when it was first introduced. Back in the day, it was primarily used to broadcast classical music, with many stations not even using any compression processing. This kept the overall audio levels much lower than they are today.

Nowadays, the modulation is pushed right to the limits, creating that overly "loud" effect, with little down time in between peaks. By comparison then, based on today's FM broadcast levels, the phono levels will likely seem much lower.

If the phono inputs still have enough gain to drive the amplifier to full usable power output, then again, there is likely nothing wrong.

A solution would be to install small output level controls on the FM section, so that it could be adjusted down to match that of the phono section.

Dave
 
That's what I was thinking or hoping. Before I sent it out, it did seem to be level across all functions but I didn't want to chance burning it up before having it gone over and realigned. I am most happy that all the original tubes tested fine.

I have the antenna on the LOC terminals and it pulls in stations I never even heard before. This is one sensitive unit.

Also, it seems after 15-20 minutes, the FM gets even louder once the tubes reach broiling temperature. Those output tubes are HOT!!! I measured 175 degrees!

I really do love this receiver. I've also got a '56 RCA Mark I console but I'd trade that in for a Fisher console in a heartbeat! Of course, it'd have to be a 1963 President...
 
Hey- I have a 500b, and a volpot from Oppat as well. I agree, the FM source is almost insanely loud at the lowest volume. Like, party-time loud. NPR anyone? :banana:

The output-level control idea in the FM section seems like a nice idea...to be honest though, coming up with the plans for this from scratch is beyond my current knowledge.
 
So maybe this is the "New Normal". No way am I going to go modifying the FM stage. I also notice since the redo that the MPX Filter hardly makes a difference now.

I also prefer to use the Loudness Contour. It really gives a richness to everything. Turning it Off makes a slight decrease in the volume but the tone is nowhere near as rich.
 
The MPX filter should make little difference in sound. FM stereo works because of an AM sub-signal containing the stereo information (L-R) that's used (in part) with the main (L+R) audio signal to modulate the FM transmitter sending out the signal that your tuner receives. We all know that AM signals can surely get noisy as the signal becomes weak, which is why a weak FM stereo signal becomes noisy, yet the same station is crystal clear when the tuner is set to receive only the main audio (mono) portion of the signal. It is the noise from the AM portion of the FM stereo signal that you are hearing. The MPX filter works by minimizing any noise generated in the AM portion of the FM stereo signal.

Adding level controls at the output of the MPX unit would likely not be very hard to implement.

Dave
 
A 50-year-old receiver designed around the broadcasting technology of 50 years ago...

I'm leaving it alone and start enjoying it. Maybe even grill some hot dogs on those tubes this weekend!

BTW: this should probably go in a separate thread but it came with 3 complete knobs with caps. All of them have the black line. I had to get 4 replacements for the rest of the knobs. Three of the knobs have a notch to accept the indent for the black indicator mark and the tuner knob has none as it shouldn't have the position indicator.

I've seen a lot of these sets with all plain caps. Which is correct? The serial # on mine is 39171 so it may be late production.
 
...I agree, the FM source is almost insanely loud at the lowest volume. Like, party-time loud...

I don't understand. When you turn the volume down the volume should be zero. Are you saying that when you turn it all the way down it's still loud??

There is no relationship between the volume "setting" when listening to FM and listening to records. It's perfectly normal for the volume "number" to be much lower on FM and higher when on Phono.
 
I can turn the volume completely down and the unit is silent just before the power switch cuts the power. At position 1 on the dial, the radio is sufficiently loud. To achieve the same volume level on any other function--tape, aux or phono--it needs to be increased to around 2.

I had the opposite on my RCA console. On that, the phono was too loud and would distort. I cured that by installing a potentiometer between the preamp and the tuner.
 
I can turn the volume completely down and the unit is silent just before the power switch cuts the power. At position 1 on the dial, the radio is sufficiently loud. To achieve the same volume level on any other function--tape, aux or phono--it needs to be increased to around 2...

That's perfectly normal.
 
Yeah, those positions for those volumes are normal.
If it bugs you, I suggest that you pop the knob indicator by putting a thin screwdriver into the back of the knob to unseat the glue.
Once the bright is off, line it up so that with the switch off, the line is at approximately the first dot at the 7:00 o'clock position and then reglue it on.
 
This is my first Fisher and I appreciate everyone's help! I did think there could be something not quite right but you guys know better than I!

It IS a bit irritating especially if I forget to turn it down before flipping back to the radio and it scares all the neighborhood pets and cracks the plaster a little more.

It is what it is.

I'll try to post some pictures of it tonight.
 
I don't understand. When you turn the volume down the volume should be zero. Are you saying that when you turn it all the way down it's still loud??

Oh - no, sorry for the confusion. When the volume is down, it's silent. When on FM, and turning the volpot up slowwwwwlllyyy, the minimum audible FM pink noise from 1 meter away is about 77-78dB, give or take. This was done using one speaker at a time (balance all the way left, or all the way right) with the switch set to mono. ***I should add one disclaimer- at the VERY minimum audible setting, I have a channel imbalance, so I have to turn the volume up a ever so slightly...it's sensitive!...to get both channels to come in evenly. This may account for the slightly higher volume...not sure.)***

I have a similar situation in the aux connection. With pink noise, the right channel comes in at about 65dB, and the left channel comes in as you turn the volpot up a tiny bit, and starts at around 65/66dB. At this point though, the left channel is now ~72dB! So, I'm having a channel imbalance problem too.


walyfd- do you have a similar problem, or do you find that both channels come in evenly? Also, is your aux connection about as loud as your FM? If so, it would be nice to brainstorm a solution...
 
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I don't notice an imbalance with the new pot, just that at 0.5, the radio is sufficiently loud for background music. To achieve the same in other functions, 1.5-2 on the dial is about comparable. I have the Channel B phono (right speaker) adjusted to the max and the Channel A is backed off about 1/4 turn to balance that out. Best compromise.

Before I got the new pot from Mark, I noticed one channel was off. Eventually, the original pot went and I had to replace it.
 
Input voltage on each input will be different too which accounts for a lot. Magnetic phono is the weakest, and why there is a Phono preamp to bring it up to almost the line level inputs (AUX, TAPE, ETC). There should be no real imbalance between AUX, TAPE, Radio as they are all line level inputs. The TAPE HEAD input however is different. Very much like a Magnetic phono except no RIAA eq.

Recap the signal path and a lot of the imbalance should dissipate. Then go after the pots, switches, etc.

Larry
 
I just had it redone about 3 months ago by a Fisher shop. I did have it up and running before I sent it off for the recap. I really can't remember how it was BEFORE the rebuild.

Here's a photo of it. Not sure if this cover is Fisher or not. Whatever it is, it's well made perforated stainless. The Garrard "A" is an ebay purchase.
 

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Nice Industrial Look. No the cover is not FISHER. It's custom made by someone. I love the Cake-Tin cover on the Garrard.

Larry
 
What I figured with the Fisher cover. It really is nicely done and fits well. The original owner was a NYC policeman so maybe somebody in the New York area was making them. If anybody ever comes across another like it, we'll have to compare.

The Garrard came with the cover and base which was why I bid on it. A cover in decent shape is very hard to come by, so this was the total package.

Here they are on top of the RCA Mark I. Doubt they're staying here but it would be convenient.
 

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that MARK 1 is GORGEOUS!!!! Do you have the companion speaker to go with it? or was that later. Looks to me to be about 58-60. I've got a '57/'58 SHF-5 in Mahoghany.

Larry
 
Yes, I have the speaker. It is currently in the basement, safely tucked away until I get the woofer reconed and get rid of some furniture! Together, it takes up a LOT of real estate. That was a thrift store find in 1998 when I was living in Virginia. Had I known then what I know now, I could have had a house full of high quality equipment. I couldn't walk into a shop without seeing something.

The Mark I was 1956 and '57. The SHF1 from '58 was the 3-piece unit with stereo tape but mono phonograph. These used an ESL Soloist moving coil cartridge and 2N104 transistorized phono preamp which allowed for an equalization switch for Ortho (RIAA), LP, AES and 78. Not sure if the 6HF1 was the first console to come with r2r but it was one of the first. They were the first transistorized units.

That's why I need the Fisher. I need STEREO! The Mono-strosity is fun but it's, well, MONO!

I'd give them both up for an elusive President, though.
 
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