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Post subject: Re: 1970 Bronco
Posted: Thu Jul 13, 2017 6:44 pm
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Very much appreciated.


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Post subject: Re: 1970 Bronco
Posted: Fri Jul 14, 2017 7:34 am
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Material located -- sized, cut, and packed for shipment.

I'll get it out in the mail on Monday.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 1970 Bronco
Posted: Fri Jul 14, 2017 10:23 am
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Cant say thank you enough... :mrgreen:
I will leave the beast apart until then.

Gonna put a 1k MO(470-ohm didn't drop the screen lower than the plate) screen grid resistor on V3 and that's it, may not be necessary(amp worked/sounded fine) but I will feel better about it.


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Post subject: Re: 1970 Bronco
Posted: Mon Jul 17, 2017 6:26 pm
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Well I got tired of looking at it apart; so I put it together and played it for a while today for about an hour. Really has a good clean tone and the tremolo is a real beast but the speaker has a hard time handling hard pick attack on chords/multi string notes. I will try doping the speaker since it really does sound good clean or playing single notes. I'm not sure if a tone stack adjustment would help the issue. I have a 5v4ga rectifier tube on the way to try a little more power/less SAG, that might help. If that doesn't work out I'll be looking for suggestions.
I'm gonna pull the 1k Screen resistor off to see if that's what is causing the issue, since I didn't remember it squashing the chords on the 1st fire up w/ a heavy attack.


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Post subject: Re: 1970 Bronco
Posted: Tue Jul 18, 2017 1:22 am
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Eric,

The main difference between the tweed Champ 5E1 and 5F1 circuit is a 10k-ohm resistor replaced a 4H choke (going from 5E1 to 5F1).

A choke could make the power a bit stouter and less "saggy." Everything else being constant. The Hammond 194A seems to come closest to these original chokes. Replace the 10k-ohm resistor with the 194A, inline with the PSU and output tranny. You may need to play with resistors to get B+ into range (~305 to 325 VDC).

I know the DCR of the choke is quoted at 167ohms. But, the impedance is what counts. And that is a function of the time-constants within the PSU, when charged. So, you'll need to measure any changes in voltage --- with the choke substitution & amp hot. Adjust resistance, if necessary.

http://www.hammondmfg.com/pdf/EDB194A.pdf

5E1:
http://ampwares.com/schematics/champ_5e1.pdf

5F1:
http://ampwares.com/schematics/champ_5f1.pdf


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Post subject: Re: 1970 Bronco
Posted: Tue Jul 18, 2017 10:17 am
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Thanks for the info.
I think the 5v4ga will help the power supply w/ less voltage sag, it'll just depend on how much it raises voltages as to going w/ a choke or trying to get better numbers w/ resistors. I still have the brown box, if necessary to lower the input side of things to find a good balance point.
Right now the V3P4screen grid&V2P6 is about 12-15 volts to high and V1 plates are 15v higher than optimal.
I should have the 5v4ga later in the week, so I'll re-measure everything and go from there.
I think the Bronco wants less SAG to operate optimally.


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Post subject: Re: 1970 Bronco
Posted: Mon Jul 24, 2017 7:30 pm
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Well its apart again and I'm almost ready to Install the Tolex (tanks again Arjay).
I received all the supplies that I needed to get back to work.
Image
The new Tolex cut to size, the width overlaps the old Tolex by about an 1". It'll stand out as being new 4 sure.
Image
The quart size can of DAP-Weldwood(red label) dries to an amber color and will be used to affix the largest area of the Tolex. To about an inch from all sides to allow an area to hold onto for placement.
The 3oz bottle of DAP-Weldwood(red label) dries to a clear color and will be used to affix the stray areas of Tolex that are loose from the sides to the corner overlaps and to finish the inch border.
The Acetone & 3oz DAP is going to be used as recommended by the fine folks at Weber speakers in a 1:1 ratio to DOPE a speaker
Image
The tools needed to prep the cabinet.
I used 100 grit general purpose sandpaper followed by 0000 steel wool to remove old glue, dirt followed by a good brush out. Before removing the old glides measure where they are, these are 15" center to center and 5 1/4" respectively. Removing the Glides and staples can be a PITA, usually the staples will break(hammer the stuck pieces into the cab flush). The glides come up pretty easily; better to pry from underneath the Tolex than from in-between the glide and tolex(prevents tearing).
Image
Removing the old Glides, reveals areas of loose Tolex that was held down w/ the glides/staples. Holes should be filled w/ filler or a concoction of sawdust and wood glue. I went to grab my can of filler only to find it solid as a rock. A good point to stop for the day, take account of what materials I may need to complete the rest of the installation.
Image


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Post subject: Re: 1970 Bronco
Posted: Mon Jul 24, 2017 9:34 pm
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Nice DIY photos! Like that new Weller iron. Is it the 35 watt model? I finally broke down and got the WESD 51 station. The digital temp adjustment is nice for both P2P and circuit board work. Esp work on delicate SMD and IC boards.

This is after nearly 25 years with the original 40-watt WLC-100 station. Love the way Wellers last and the number of replacement tips that are available.

What kinda 60/40 solder is that? I like Kester or Wonder Solder.

:)


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Post subject: Re: 1970 Bronco
Posted: Tue Jul 25, 2017 8:06 am
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Quote:
Nice DIY photos! Like that new Weller iron. Is it the 35 watt model? I finally broke down and got the WESD 51 station. The digital temp adjustment is nice for both P2P and circuit board work. Esp work on delicate SMD and IC boards.

This is after nearly 25 years with the original 40-watt WLC-100 station. Love the way Wellers last and the number of replacement tips that are available.

What kinda 60/40 solder is that? I like Kester or Wonder Solder.

Thanks, I don't take great pics and have ZERO experience w/ upholstery application. So, total beginner DIY Tolex job and proceeding slowly w/ extreme caution. Hazard area is the sticking, you only get one shot.
No, I think they discontinued the 35watt pencil(relabeled due to only being 33w). Its 33watts and I bought a few spare tips.
The solder is Worthington 60/40 Rosin core .031", the site I purchased from didn't have Kester.
I may piecemeal my way to a WESD51 soldering station w/ a couple swap-out parts in the future.


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Post subject: Re: 1970 Bronco
Posted: Tue Jul 25, 2017 1:01 pm
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More prep-work, wood filler. At minimum, fill the holes where the glides feet were(you'll likely hit very near these holes if the glides go back in the right location). Fender used filler as can be seen in these pics in the finger joins(grey looking filler) the new filler is a bit darker.
Image
I used hobby sticks(pop-cycle) to press the filler into the holes. I bought the smallest tube of filler I could find to fill my needs for the project, the stuff wont last forever on your shelf even if sealed tightly.

Next step after sanding any standout filler is to adhere loose side pieces, I'll wait the full 24hr suggested hardening time for the filler.


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Post subject: Re: 1970 Bronco
Posted: Wed Jul 26, 2017 11:28 am
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Lightly sanded the wood filler, then applied the DAP-Weldwood (clear-dry) to the pine and the Tolex backing from the side pieces. Waited a few minutes to allow the glue to start setting up and mated the surfaces. Used mineral spirits to clean the big drips that inevitably land where you don't expect or want(hairy areas of the feet, etc). Used those pop-cycle sticks again to help press the edges down snug, keeps the glue off your fingertips!
Image
Also used some painters tape on the outside of the Tolex, to keep the glue from seeping out of the holes made by the glides spikes and the staple holes. The corner cut flaps and a few other loose pieces were also re-glued. I don't think the corners will look that good at this point but will wait and see the final product before judging my work. That completes all the prep work, sans dry time.


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Post subject: Re: 1970 Bronco
Posted: Thu Jul 27, 2017 7:00 am
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The prep work is never done!
So, I started my layout procedures. Measuring, re-measuring, taping and marking. Centers and edge end points will help ensure I get it done right. Ready to share a pic of my layout, after I recharge my camera battery.
May take a couple hours to recharge enough for a couple photos.
Tools & front of Tolex w/ registration marks, cabinet taped w/ center and end marks
Image
Back of Tolex, taped off working area
Image

Well, I stuck and rolled it after lunch. Weighted and drying/curing.
The observations I can make thus far is that if you do this in your living room like I did, turn the ceiling fan on its lowest setting or off. It really speeds the drying action to much. If you put something weighted on top of the Tolex, make sure it isn't a reactive material as some off gassing and heat is generated during the curing of the adhesive. An uncovered/treated piece of 1/2" smooth plywood w/ several bricks on top would surely work well here.


Last edited by sfceric64 on Fri Jul 28, 2017 11:18 am, edited 1 time in total.

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Post subject: Re: 1970 Bronco
Posted: Fri Jul 28, 2017 11:12 am
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Let cure overnight but was tempted to glue down the wings after a couple beers, thought about it over a couple more beers and came to my senses. It was a good thing I did; as I needed to trim one end as the length stretched about an 1/8" beyond my registration marks. While rolling out the Tolex, they suggest 25lbs per inch of contact pressure. They make tools for this, I don't have one any longer. So I used a standard 2" dowel rod from the closet, it worked very well. This morning laid down the clear dry glue for the remaining wing areas, currently drying again(much like watching the grass grow). I tried again using mineral spirits and acetone to remove the small blob of adhesive from the bottom front of the grill cloth w/o any luck.
Four more pics to follow:
Without glides
Image
With new glides
Image
Inside cab wings
Image
Completely assembled

Before final assembly I will try rolling in a couple 5v4st's. I picked up an RCA(arrived yesterday) and a Sylvannia due maybe today. Both are large shouldered tubes over 4" seated. Will ensure the voltages aren't to outta line
and check the playing dynamics. Not expecting to much being a single ended amp but thought I would try it here first just to experiment w/ the voltage increase.


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Post subject: Re: 1970 Bronco
Posted: Fri Jul 28, 2017 6:42 pm
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Eric,

Nice job. This is your first attempt at Tolex fixes? Very good, indeed! :)


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Post subject: Re: 1970 Bronco
Posted: Fri Jul 28, 2017 9:06 pm
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Yeah that was my cherry, thanks.
Much respect for those guys back in Fullerton in the early days of Fender. Those buildings had to have made really difficult working conditions w/ all the sawdust and glue.
In retrospect, I should have redone the whole amplifier. Maybe next time.
And thanks again to Arjay for supplying some of his stash to make it all possible.


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