All original 500B - love it or leave it?

[larryderouin]

Tech should be aware of ANY ELECTROLYTICS branded "FRAKO" or "DUCATI". Rubber end seals either bulging or disintegrating. These are "NUKE ON SIGHT", period! All are axial type.

That 1.2kΩ/7W "green bean" Rocky hill alludes to gets replaced with a 10w. https://www.mouser.com/ProductDetail/588-20J1K2E

 

[calman46]

You need to protect the on/0ff switch. Does McShane's kit come with the inrush current limiter? All the electrolytic caps should be replaced, it's not worth the risk not to. The original sonic signature is long gone.

 

[Lewish]

That makes sense to keep the original sonic signature. As I get more into this, I'm also less inclined to do the 'shotgun' approach on the more vintage pieces.

I did the McShane kit a fair while ago and believe a good portion of the caps were the orange drop type and it did also come with some 'russian' PIO caps.

If I recall correctly, that 1.2ohm green resistor (looks like a skinny green bean top/left in your first couple of photos, post #11) is one of the components that may need to be refreshed due to age/drift.

If you search around, there's a thread on setting the phase inverter to dial that portion in, if needed.

edit... Below is a picture where I had labeled the parts to be replaced by Jim's kit, if it helps to check components.

So I got the work done and the only tubes I need right now are for the drivers so I have a fondness for when there was British quality with NOS Mullards https://www.tubedepot.com/products/12at7-ecc81-mullard

 

[larryderouin]

12AT7/ecc81 in drivers is not Correct. 12AX7/ecc83 is specified for all preamp, tone control, driver/phase inverters. If you have Tele's anywhere stick them in V-11 & 12. Make sure the sections match in emissions and gm. Otherwise in all other tube you can use Russian tubes to good advantage..... (ie: wallet does squeal like a pig with it's throat cut!) SOVTEK 12AX7 LPS most guys that have them talk highly of them in phono section and use the older tubes else where.

 

[Lewish]

12AT7/ecc81 in drivers is not Correct. 12AX7/ecc83 is specified for all preamp, tone control, driver/phase inverters. If you have Tele's anywhere stick them in V-11 & 12. Make sure the sections match in emissions and gm. Otherwise in all other tube you can use Russian tubes to good advantage..... (ie: wallet does squeal like a pig with it's throat cut!) SOVTEK 12AX7 LPS most guys that have them talk highly of them in phono section and use the older tubes else where.

 

[Lewish]

Here is the serviced unit, which sounds amazing. I have 12AX7 Realistic Japanese tubes for some reason in the drivers and so am looking at replacing those. All the other tubes tested in the 90 - 95% range and it is clear this was a well cared for lightly used Fisher 500B

 

[larryderouin]

Those Japanese Realistics are usually Matsushita'a which are pretty darn good (they used Mullard tooling, look for 4 seams on top at 90* from each other). Swap them with the phono tubes if the Phono tubes are Tele's. and re-listen. OR just leave them in where they are.

 

[Lewish]

Those Japanese Realistics are usually Matsushita'a which are pretty darn good (they used Mullard tooling, look for 4 seams on top at 90* from each other). Swap them with the phono tubes if the Phono tubes are Tele's. and re-listen. OR just leave them in where they are.

Thanks, very helpful. I am glad my tubes tested do well after starting to look around and seeing the prices! I think I will get used to the way it is currently, I found a great tech and invested $450 in the service. It sounds amazing and I know it is only just breaking in the new caps and so on. Very pleased.

 

[Lewish]

Congrats on the 500B

If you take detailed pictures of the guts of the unit from the bottom, the knowledgeable folks on this forum should be able to what work has already been done and if components have been refreshed.

If they guy was thorough and did recently service it, you might be pleasantly surprised.

This is the finished restoration.

 

[Sam08861]

Looking good Lewish! Enjoy!

I wasn't an avid FM listener until I got mine, so give that a shot if you haven't already.

 

[RS Steve]

I'm not seeing any adjustable bias, no inrush limiter to protect the power switch, no sampling resistors, no screen stability resistors, can capacitors still in connection with discreet capacitors added to them, and original death capacitors still in place.

 

[Lewish]

I'm not seeing any adjustable bias, no inrush limiter to protect the power switch, no sampling resistors, no screen stability resistors, can capacitors still in connection with discreet capacitors added to them, and original death capacitors still in place.

I trust my tech, he is very well versed in Fishers. This unit was in mint condition and so we tested everything. Decided to pass on the inrush limiter, power switch testing fine.

 

[RS Steve]

I trust my tech, he is very well versed in Fishers. This unit was in mint condition and so we tested everything. Decided to pass on the inrush limiter, power switch testing fine.

You don't install an inrush limiter because your switch is bad, it's to protect it from going bad. The power switch is one of the most common failures on these wonderful receivers, and options to replace them very limited. Plus, the inrush limiter drops the incoming voltage almost two volts which helps with the wall voltage that is higher these days, and can cause tubes to run hotter than they should. No bias adjustment, or sampling resistors means you have no way of knowing what bias voltage the tubes are operating at. You can't install modern production output tubes in the future without them burning up since they require much more negative voltage than originals. I never understood piggybacking new capacitors onto the original can capacitors since the old capacitors can still short out from age. These things I mention are all things most of us do to give these units another 60+ years of reliability, instead of just keeping it running until an old component gives out. But as long as you're happy with it, that's all that matters.

 

[Lewish]

I trust my tech, he is very well versed in Fishers. This unit was in mint condition and so we tested everything. Decided to pass on the inrush limiter, power switch testing fine.

Looking good Lewish! Enjoy!

I wasn't an avid FM listener until I got mine, so give that a shot if you haven't already.

The FM is incredible! First thing I listened to and love the tuning eye.

 

[Lewish]

You don't install an inrush limiter because your switch is bad, it's to protect it from going bad. The power switch is one of the most common failures on these wonderful receivers, and options to replace them very limited. Plus, the inrush limiter drops the incoming voltage almost two volts which helps with the wall voltage that is higher these days, and can cause tubes to run hotter than they should. No bias adjustment, or sampling resistors means you have no way of knowing what bias voltage the tubes are operating at. You can't install modern production output tubes in the future without them burning up since they require much more negative voltage than originals. I never understood piggybacking new capacitors onto the original can capacitors since the old capacitors can still short out from age. These things I mention are all things most of us do to give these units another 60+ years of reliability, instead of just keeping it running until an old component gives out. But as long as you're happy with it, that's all that matters.

Thanks, I will ask.

 

[AlTinkster92]

Steve is absolutely correct on the current limiter protecting the volume pot and switch, personally Id go a step farther and use a bucking transformer to keep those nasty high wall voltages at bay. My 2 cents...

 

[jvstratman]

The inrush current limiter will lower the voltage few volts and that's a good thing but, as it's name implies, it limits the current by electrically absorbing some of it when you switch the reciever on/off. This results in less of an arc at the switches internal contacts. Those contacts burn and lose the ability to maintain good contact.

 

[Weld Engr]

I’m a novice at best and with a lot of help on here from very experienced people I restored my 800-B. Some simple safety devices are being recommended to protect your investment. The inrush limiter and screen resistor protect $$ parts I also use a variac to drop my 122-123 V wall voltage to around 117V a bucking transformer is another option. I subscribe to the notion any good tech or engineer should be open to suggestions. It’s your money I think the guys on here just hate to see something preventable happen to such a nice unit.

 

[Lewish]

I’m a novice at best and with a lot of help on here from very experienced people I restored my 800-B. Some simple safety devices are being recommended to protect your investment. The inrush limiter and screen resistor protect $$ parts I also use a variac to drop my 122-123 V wall voltage to around 117V a bucking transformer is another option. I subscribe to the notion any good tech or engineer should be open to suggestions. It’s your money I think the guys on here just hate to see something preventable happen to such a nice unit.

Hi: I have been really happy to get such great information. I appreciate everyone's help here and advice. As I can't do the work myself I am relying on my local tech who is one of the better techs I have come across since I got into collecting vintage gear ten years ago. He has a great deal of experience with these Fishers and so I am going to post his thoughts on your feedback here. I will get the Variac and set the voltage to 117. Importantly everything in this unit was extraordinarily well maintained by its original owner who was a talented technician. The tubes all test above 90%, many above 95% and everything that was not changed was testing at spec and looking like new. So my tech has never seen a Fisher in this good condition after working on over 500 Fisher units over his 40 years. He is in demand for very specialized work and really knows his stuff so I have confidence in him still knowing many of you may continue to disagree. The rectifier and a bunch of other work got done within a few days of me leaving it with him so the service and turn around was excellent. And I am very happy with the work and how this sounds.

"The only real value in installing adjustable bias & cathode resistors for measuring, and things like "screen stability resistors" is to make it easier to use horrible asian/ex-soviet "7591" output tubes(which are really just their awful 6L6 copies in 7591 physical format). With American made, real 7591 tubes, especially original issue like yours, there is no practical need for the above. They bias generally quite close enough to be well in range, and don't have any stability issues(and unit does already have gridstopper resistors on the 7591s). And, yes, doing those changes would have been expensive, and a real pain for me to do. I have a really hard time doing painful things when I know there's no compelling practical reason to do it.

The two major reasons I left the original chassis can supply caps connected are that 1)these virtually never die violently, i.e., shorting, rather, simply dry up & lose capacity, so may as well use their extra capacity while they last(~10-20 years), and 2)No replacement chassis cans are made by anyone with a long track record, thus untrustworthy.

And you're correct on the inrush current limiter. To give any meaningful prolongment of switch life, the ICL would have to be of higher than normal cold resistance, so would be *noticeably* bad for sound. An ICL that has a hard-to-notice effect on sound is too low cold resistance to do anything whatsoever to prolong switch life."

So there you have it. I offer this as me being caught between the tech and my Fisher Forum friends and I have spent $750 on the receiver and $450 to do the important maintenance as far as I can right now on a family budget. I respect what everyone is saying here and I will keep you posted as I go forward.

What I hear through the Del Mars is audio nirvana and I am delighted to have a mint Fisher 500B that is the most important thing right now.

 

[Lewish]

You don't install an inrush limiter because your switch is bad, it's to protect it from going bad. The power switch is one of the most common failures on these wonderful receivers, and options to replace them very limited. Plus, the inrush limiter drops the incoming voltage almost two volts which helps with the wall voltage that is higher these days, and can cause tubes to run hotter than they should. No bias adjustment, or sampling resistors means you have no way of knowing what bias voltage the tubes are operating at. You can't install modern production output tubes in the future without them burning up since they require much more negative voltage than originals. I never understood piggybacking new capacitors onto the original can capacitors since the old capacitors can still short out from age. These things I mention are all things most of us do to give these units another 60+ years of reliability, instead of just keeping it running until an old component gives out. But as long as you're happy with it, that's all that matters.

Hi Steve: I got a variac and turn it up slowly each power up. Running at 117. The one thing I am noticing is a hum on the phono stage. I adjusted the volume on the back but wondering if there is a known cause of the hum in the audio stage.