'54 5e3 restoration

[Stephen1966]

It lives... Still plenty of work to do, but there is a functional and decent sounding amp. One of the power tubes was leaky, the board is slightly conductive, and one or more of the coupling caps might be starting to go leaky, haven't tested out of circuit yet. The original bias resistor was a bit low, might order a nice enameled one that looks more the part. Installed larger dropping resistors. Pots are relatively clean, all of the remaining resistors were within like 3%. Not much hum. I think its a good start...

Cap stuffing went well, even if some of you find it distasteful. Can't really tell anything was changed without desoldering and looking at the cut on the bottom, unless you notice how shiny the new wires are, or that I didn't have the correct value cardboard tube for one of them. Hard to get a picture where you can see seams or drills. New Nichicons and Vishays are way lighter than the originals, so I'm not worried about things snapping again.

It's very hot, and very humid here, so worst time of year for fiberboards. I will spend some more time with IPA and see how much I can improve things. Hopefully, I can avoid pulling the board all the way.

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Looking good - I'm curious, how did the yellow Astrons test?

Now this is going to be controversial, but you have a grounded core mains lead going to the ground switch which I'm assuming now operates as a standby switch. What is your view on restoring the death cap as a noise filter/ground lift a la Bassman 100 https://robrobinette.com/Death_Cap_and_ ... Switch.htm there are other ways you might elevate the heater voltage to mitigate hum but you're leaning towards the authentic and this is a safer alternative to the original death cap on a two-way switch.

[bepone]

nice to see 500v radial nichicon cap, i was searching this for a years!

progress in a good way for us 450->500V
also nowadays there is a progress in development of 600V electrolytics too, so no need anymore in serial cap connections, good future in amp building

[maxkracht]

nice to see 500v radial nichicon cap, i was searching this for a years!

I have been using them for years, perhaps they are harder to find where you are? 10k+ hr rated at 105c. Have yet to see one fail. I usually stick with the 450v with a better ripple current rating unless 500 is necessary, but I use similar Nichicons almost exclusively in new builds.

I'm curious, how did the yellow Astrons test?

Haven't tested very much. I am getting, up to, a bit over .5v on the first two coupling caps depending on where the volume knob is. Not sure what the deal is, but the board is conductive so I don't trust any readings in circuit. The printing on those astrons comes off with alcohol, so need to lift them to soak the board anyway and will see what the lcr meter says. Will probably pull out the backer board and wash that too. I don't want to put in orange drops like bepone suggests, but It might come to that. Thought I had a more complete set of functional astrons, but only found a couple .01 and .27. Can always replace a .1 with the .05uf death cap. I prefer a bit less bass anyway...

I pushed this project ahead of some others and probably need to do some other repairs today so people don't get mad at me. Will get back to it this weekend.

you have a grounded core mains lead going to the ground switch

I just haven't gotten to that yet. I always disconnect ground switch/death cap unless requested by the owner, and I have a stash of class Y caps if they are insistent on keeping it. I usually sweeten the deal by using the ground switch for a mod, but probably won't do that in this instance.

[Stephen1966]

I am getting, up to, a bit over .5v on the first two coupling caps depending on where the volume knob is.

So the volume knobs are probably behaving like voltage dividers, TONE probably affects it as well, but .5VDC isn't good. If your board is conductive it's one thing but can you test to see if the voltage is being elevated by AC? Just swapping out the caps for some known good ones temporarily might be an easier place to start.

This project is great. But if you are too busy, you can always send it over here

[maxkracht]

All of the caps were bad… My nicer lcr meter says esr is around 50-200 ohms at 1kHz. For reference, new caps are around 6 ohms. Cheapy meter says about 3% v loss on every cap, so no good at all. The red cap was a bit leaky, but works well enough, and domino tested perfectly. The current owner played the amp a bit when he bought it and said it sounded bad. Not sure how long he played it, but maybe no screen/preamp caps along with an undersized dropping resistor put too much stress on the coupling caps? I expected a couple of leaky caps, but all is unusual in my experience. The death cap was not leaky.



The owner didn’t want any fancy replacements, just wanted yellow axials. Trying out some Vishays for the first time. On the ones I tested for this project, outside foil is the opposite of the line that I thought might indicate outside foil. So, just decoration?



Lots of IPA and scrubbing, and a bit of heat gun/desiccant later, no more conductive board. New caps in, new power cord wired a bit nicer, fuses and backup diodes on the HT, everything is sounding and working as expected. I put the original bias resistor back in. It's a little under 250ohms, but puts the bias just under 100% so I am calling that fine.
 That's part of the charm, right?

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[maxkracht]

Anyone know what these wood plugs are for? Indexing to route the control panel? Some kind of clamping operation? Seems too symmetrical to be a coincidence.

[sluckey]

Most likely dowels that are at least as long as that cutout. That's a very weak point in the top piece of pine especially with the weight of the chassis hanging on that narrow piece of wood. The dowels reinforce that weak section.

[maxkracht]

Most likely dowels that are at least as long as that cutout. That's a very weak point in the top piece of pine especially with the weight of the chassis hanging on that narrow piece of wood. The dowels reinforce that weak section.

Interesting, thank you. I guess that section would be prone to splitting from the finger joint side or the screw/routed corner side. I wonder how many modern versions have a dowel or spline in that location. Nice place to add a "decorative" stripe or two on a hardwood cabinet.

[Stephen1966]

Anyone know what these wood plugs are for? Indexing to route the control panel? Some kind of clamping operation? Seems too symmetrical to be a coincidence.

Great work - I bet its sounding really nice now - Chrysler-Car-Door speaker notwithstanding Shame about the yellow Astrons - I had my fingers crossed for you - but when they're as old as Methuselah I guess it's to be expected. I see the Mica cap is still there though. Still good?

The dowels are reinforcement. The grain runs length-ways across the top and the cutout is pretty deep so I guess when Fender started getting returns because people made the mistake of sitting on them, breaking the tops, they looked for ways to reinforcing the those "ears". This is an early cab though so maybe they didn't wait for the returns to start pouring in. Or maybe it was because of troubles with different, earlier cabs. The dowel, running perpendicular to the grain just adds a little strength. The reason I think it may have been an afterthought, is because it isn't shown in the plans for the cab. This was done by Fender though. Can't remember where now, but I've seen similar restoration videos online where they talk about it.

[Stephen1966]

My nicer lcr meter says esr is around 50-200 ohms at 1kHz.

You're more likely to get "datasheet " values if you test at 100Hz (120Hz). Good catch though, saw the comment about the "domino" as well.

[maxkracht]

You're more likely to get "datasheet " values if you test at 100Hz (120Hz). Good catch though, saw the comment about the "domino" as well.

Data sheet values? I usually test electros at 100Hz, but the first frequency my meter tries is 1k so I am relatively used to those numbers. Red Astron cap is definitely bad, but not much voltage going through there and the tone control still controls tone well enough. Not perfect, but the amp sounds very good in spite of this and the difference is probably only slightly noticeable on extreme tone settings.

[Stephen1966]

You're more likely to get "datasheet " values if you test at 100Hz (120Hz). Good catch though, saw the comment about the "domino" as well.

Data sheet values? I usually test electros at 100Hz, but the first frequency my meter tries is 1k so I am relatively used to those numbers. Red Astron cap is definitely bad, but not much voltage going through there and the tone control still controls tone well enough. Not perfect, but the amp sounds very good in spite of this and the difference is probably only slightly noticeable on extreme tone settings.

Yeah! It's academic really - don't know where you would find datasheets for these artifacts - but I do find that the values across the board, capacitance, ESR, Q, tan delta etc. come in more on the money when you set the frequency to the manufacturers usual test standard which is typically 100Hz for Euro made components and 120Hz for US made. My meter's auto default is 1k as well but I put it in manual to run these kind of measurements. It's a DE-500.

The tone is massively dependant on the volumes as you know and there is interactivity between the volumes as well. For anyone else not familiar with these, the empty channel volume will inject bass into the operating channel when you turn the empty channel's volume up. I don't agree these amps are a one-trick-pony as some seem to think. When you get into it, there are many colours to explore. Can you stuff the red Astron? Or would you just replace it? If it's massively off it's going to adversely affect the high end.

[Stephen1966]

[Deleted]

[maxkracht]

Yeah! It's academic really - don't know where you would find datasheets for these artifacts - but I do find that the values across the board, capacitance, ESR, Q, tan delta etc. come in more on the money when you set the frequency to the manufacturers usual test standard which is typically 100Hz for Euro made components and 120Hz for US made. My meter's auto default is 1k as well but I put it in manual to run these kind of measurements. It's a DE-500.

Mine's a DE-5000 I treat everything as go/no-go when it comes to what needs to be replaced. I did put on kelvin clips, but mostly for style points. Accuracy is not important for what I do.

The tone is massively dependant on the volumes as you know and there is interactivity between the volumes as well. For anyone else not familiar with these, the empty channel volume will inject bass into the operating channel when you turn the empty channel's volume up. I don't agree these amps are a one-trick-pony as some seem to think. When you get into it, there are many colours to explore

First tube amp I ever built was a Mission 5E3 kit. I gigged with that thing through my 20's and really put it through its paces. Didn't feel like I was too limited in sounds with just the amp, tuner, and a volume pedal to control distortion. Good times.

Can you stuff the red Astron? Or would you just replace it? If it's massively off it's going to adversely affect the high end.

Don't think it would be easy to stuff. I have thought about making molds for blue astrons, but doubt I will ever get around to it. I work on BF/SF stuff pretty regularly. The red astron isn't that far off and I don't think the high end is suffering noticeably. This amps owner lives a few blocks from me, so I will hear about it if there are problems.

[Stephen1966]

Mine's a DE-5000

Damn! You've got the one with the extra zero - must be better. Actually, it's a typo from me, mine's a DE-5000 as well. Kelvin clips are a must have, not for style, but for getting in an amp and working on it. Best thing I did though was buy a power pack - what do you call it? - a wall wart??? That actually allows me to calibrate it and keep it switched on. The Auto-Off after 10 minutes was driving me nuts. You will get more utility out of it though if you use it in manual. Nothing wrong with accuracy. For our purposes though, when you go measuring stuff that is, it's all about kind of ball-park-ish.

First tube amp I ever built was a Mission 5E3 kit.

Really! That's great, I cut my teeth on a Tweedle-Dee and I've been playing with it again just recently. I think it was while I was building that, that I found the video on the dowels. Yeah! YouTube taught me how to cover the box. The mods in the Tweedle-Dee give more gain past 6 and more tone as well. Stick a jumper in the INST high across to BRIGHT low, plug the guitar into BRIGHT high then dial everything up to 11 it really rocks, just like a pure-bred 5E3... same kind of interaction between the two channels but a real hot rod. Great saturation, touch sensitivity and a lot of tone/break-up control with the guitar's volume knob. Don't know what kind of music you are into, but it rocks!

The red astron isn't that far off...

How far? Should be possible to calculate the cutoff. If the speaker isn't up to snuff, you might not hear much difference... but...

Of course, there's no reason other than authenticity to go with a Jenson P12, the blue alnico's are really good and a real upgrade - I think Fender did an Edge "reissue" with one of these. A bit pricier than normal stock but if you put all the good stuff in that circuit through a good speaker like that - it will be a killer. I use a Vintage 30 in mine, not everyone likes them sure, but it has a great tone to my ears.