What is this?

[init4fun]

Charlie's post is awesome advice and I'd give it two likes if I could.

The only thing I want to add here is a discussion about the capacitors Eric says he ordered. Eric, in modern times the capacitance rating on capacitors has been tweaked slightly, and I'll use your coupling caps for my example here. Your schematic specifies .047 MFD for the coupling caps, and that size has been replaced with .05 MFD as the modern equivalent. Yes you still can get .047 MFD caps but most likely at a much higher cost than the more commonly produced .05 MFD. The small difference (.003 MFD) is of absolutely no consequence in your application, just make sure you heed Charlie's advice of always going higher on cap voltage ratings and never lower. Things like using modern equivalents whenever possible and buying in bulk commonly most used sizes (like your .05) of reputable brands from reputable retailers will save you mad $$$ over the course of your hobby

 

[larryderouin]

init4fun, while your explanation is good, it's technically incorrect as to how cap values are numbers. Basically you have the values backwards. Caps used to be when I was wearing short pants numbered for example; 0.1, 0.5, 1.0, etc. About the late 60's / early 70's It changed now you have for example .22, .33, .39, .47, .56, .68, etc and most are within 10% to 20% of the tolerance limits for the old caps which could be as high as +90% to -50%.

OLD................NEW
.05mf.............. .047uf

Eric; most caps now adays come in 2 flavors.....10% value tolerance and 20% tolerance. You'll find that the transposition of the old value to the new value on your coupling caps is well within 10% of the old value spec and that's good. While you can find 5% caps they aren't necessary unless you're building an amp and resistors, diodes, etc are all 1% parts, so don't go overboard on spec's. I would recommend that you go 1-2 voltages higher on the smaller caps (<50v) as the wall voltages today are generally 10% higher than back in the late 50's/early 60's when your maggie was made.

 

[init4fun]

Well that's the second time my brain has worked in reverse in this thread, gonna have to send it out for recalibration.......

Thank You for the correction Larry

 

[REeeericB]

Charlie's post is awesome advice and I'd give it two likes if I could.

The only thing I want to add here is a discussion about the capacitors Eric says he ordered. Eric, in modern times the capacitance rating on capacitors has been tweaked slightly, and I'll use your coupling caps for my example here. Your schematic specifies .047 MFD for the coupling caps, and that size has been replaced with .05 MFD as the modern equivalent. Yes you still can get .047 MFD caps but most likely at a much higher cost than the more commonly produced .05 MFD. The small difference (.003 MFD) is of absolutely no consequence in your application, just make sure you heed Charlie's advice of always going higher on cap voltage ratings and never lower. Things like using modern equivalents whenever possible and buying in bulk commonly most used sizes (like your .05) of reputable brands from reputable retailers will save you mad $$$ over the course of your hobby

Thank you man!

init4fun, while your explanation is good, it's technically incorrect as to how cap values are numbers. Basically you have the values backwards. Caps used to be when I was wearing short pants numbered for example; 0.1, 0.5, 1.0, etc. About the late 60's / early 70's It changed now you have for example .22, .33, .39, .47, .56, .68, etc and most are within 10% to 20% of the tolerance limits for the old caps which could be as high as +90% to -50%.

OLD................NEW
.05mf.............. .047uf

Eric; most caps now adays come in 2 flavors.....10% value tolerance and 20% tolerance. You'll find that the transposition of the old value to the new value on your coupling caps is well within 10% of the old value spec and that's good. While you can find 5% caps they aren't necessary unless you're building an amp and resistors, diodes, etc are all 1% parts, so don't go overboard on spec's. I would recommend that you go 1-2 voltages higher on the smaller caps (<50v) as the wall voltages today are generally 10% higher than back in the late 50's/early 60's when your maggie was made.

Thanks for the info, it's very generous of you to take time to reply to my thread. Thank you!!

 

[REeeericB]

Charlie's post is awesome advice and I'd give it two likes if I could.

The only thing I want to add here is a discussion about the capacitors Eric says he ordered. Eric, in modern times the capacitance rating on capacitors has been tweaked slightly, and I'll use your coupling caps for my example here. Your schematic specifies .047 MFD for the coupling caps, and that size has been replaced with .05 MFD as the modern equivalent. Yes you still can get .047 MFD caps but most likely at a much higher cost than the more commonly produced .05 MFD. The small difference (.003 MFD) is of absolutely no consequence in your application, just make sure you heed Charlie's advice of always going higher on cap voltage ratings and never lower. Things like using modern equivalents whenever possible and buying in bulk commonly most used sizes (like your .05) of reputable brands from reputable retailers will save you mad $$$ over the course of your hobby

I ordered them from Antique Radio, but I haven't heard back from them, which is disappointing. So, maybe I'll look for another vendor.

 

[REeeericB]

Although I can appreciate your enthusiasm for rebuilding your 185, I would suggest that you slow down a bit and spend some time reading some of the numerous threads on here about rebuilding / modding the 175/185 and about vintage restoration in general.

At this point (which is exactly where we all started) you don't seem to know the difference between a cap and a resistor or where certain parts are located in the circuit. Do you know how to identify the pin numbers of the sockets? Or how to read a schematic? Or how to safely measure voltages? Or how to drain voltage from charged caps before you work on an amp?

I would also hold off on ordering parts until you have a handle on which types might be best. Hopefully you know that replacement caps need to be at least the same voltage (or higher) than the originals.

Ordering a few parts at a time can get expensive too. Here's one way to save on shipping:

http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562

Unless you have the equipment to test the power supply caps thoroughly (for value, electrical leakage, and ESR) you should plan on replacing them all, as well as the cathode bypass cap.

Then you need to decide whether you want to use a replacement can or individual caps mounted under the chassis. There are differences of opinion as the what's best, usually based on ease of installation. Space is one factor. Another is that, if a can is soldered to the chassis, you might need a more powerful soldering iron to remove it. There are also large differences in cost between these two approaches.

Individual caps are best sourced from a major supply house like Mouser or Digi-Key rather than some place like eBay where you are likely to find many that are poor quality or "name brands" that are actually counterfeits.

Have you measured the resistors to see if they're in spec? The carbon comp types used in these are often out of spec or barely in spec, at which point you might as well replace them. And they can be noisy even if they're in spec. Fortunately, there aren't that many parts in these console amps. I recently rebuilt a Motorola and I ended up replacing every carbon comp resistor except the grid stoppers, whose exact value isn't critical.

Another thing you might have noticed is that many of these console amps, including the 185 and the Motorola I just restored, don't have fuses. So you should learn how to wire one in correctly.

Some voltages, especially the tube heaters, will also be too high because of the higher modern wall voltage. You need to know how to deal with this.

In the case of the Motorola, it wasn't just the heaters because the amp supplied power to other components (tuner / preamp) so, without them drawing current, voltages were too high everywhere. This won't be as much of an issue if you're restoring a complete console but if you're rebuilding the amp for stand-alone use it can be. I ended up putting in an additional power supply section (another cap and dropping resistor) and changing the value of one of the existing wirewound resistors to compensate.

Bottom line . . . You certainly don't need to be an expert but, if you're not aware of issues like these, do some homework first. I'm sure you're capable of getting this amp up and running but it will be much easier, and safer, if you're better informed.

Thank you Squidward! I appreciate the time and thought that you have put into my thread!

 

[markmcmuz]

Antique Electronic Supplies? If so don't worry order will come.