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Cabinet and Chassis Restoration and Refinishing For help with cabinet or chassis restoration (non-electrical), please leave a message here. |
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23rd Jul 2018, 2:04 pm | #1 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re-Veneering a simple amp cover - a first attempt... (1)
Inspired by Steve's excellent write-up of re-veneering a stereo receiver (link), I decided to have a go at 'restoring' a damaged, but inexpensive, A&R Cambridge A60 Amp that I picked up recently on a certain auction site - the next few posts are the result:
The wooden case / cover was (as usual) worse than it seemed from the auction photos, with one end completely separate, the mitre joint having failed, a few small areas of chipped and missing veneer, not to mention plenty of general scratches, scuffs, dents, stains, chips, etc. Adding to the problem, all of the 3 constituent plywood panels had warped slightly over the years. Overall, 'tatty' might have been a better and more appropriate description. On the plus side, the amp was at least complete and original, both inside & out-, right down to the original foil screening (it's above the phono stage) and an original sticker - "Case built by: Diane". The outputs are dated 1979, so she did a pretty good job, almost 40 years ago ! |
23rd Jul 2018, 2:10 pm | #2 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
The initial repairs, essentially everything needed to get it back to a 'workable' condition, were just sanding (lots of.... with 80, 150 & 180 grades), re-gluing the separate end piece (Evo-Stik wood adhesive), and wood filler rebuilding those areas with missing veneer chips, dents, scratches, etc. I used Ronseal Wood Fillers (predominantly the 'medium' grade), which behaved exactly as Steve described in his earlier thread. Just re-gluing the end piece was probably the most difficult step, although a pair of 90 degree corner clamps helped immensely - the repaired joint is not perfect, but it's as close as it would go with the warp that's present (part of a filled edge of the rebuilt joint is visible in the 2nd. photo below - for scale, the filled 'seam' is < 1mm wide).
How do you correct slight warping on plywood panels such as these ? steam & clamps ? I could probably have stopped at this stage, and just used a stain / finish to mask the remaining marks, but having read Steve's veneering thread, several times,.....and exchanged a few emails directly, the veneer (eBay, paper backed, 0.6mm) & glue (Titebond Cold Press for Veneer) were ordered. |
23rd Jul 2018, 2:18 pm | #3 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
I decided the best option was to veneer the end pieces first, followed by the top piece, to cover the glue lines of the new end panel veneers, and finally the narrow 'front' veneer edge strips. As Steve mentioned several times, it pays to think everything through well in advance, and even dry fit where possible. I'd selected the area of the veneer sheet I wanted to use for all of the panels, to be able to 'wrap' the wood grain around the corners as it were, but I did over-estimate the 'spare' amount to add for trimming - only ca. 1 maybe 2 mm extra is really necessary; with a 'plain' veneer it wouldn't really matter, but when trying to wrap the grain around a corner, it gets much more interesting if you're cutting the parts over-size, and thus effectively removing wood grain from the area of the corner join. As it happens, I benefited from a good measure of old fashioned luck.... having only realized this last point after cutting the veneer panels.
The veneering went very smoothly: once the glued veneer was in position, I just used a narrow, rigid, wallpaper seam roller (ca. 2" wide), to press the veneer down everywhere, before finally clamping in position for several hours, using Cling-film to prevent glue transfer anywhere else. There was no evidence of glue seeping through at all, despite a (more than) generous application to both surfaces. Trimming was also largely pain-free, using just a sharp hobby knife for the initial cuts, and 180 & 240 grade sandpapers, on a small wooden block, to finish to size - the only area of particular note was in sanding the ends of the large top veneer to size (the sides pieces being already in place). These were done in the same way, but using firstly, a layer of insulating tape to protect the show surface of the end panels during sanding, and subsequently, a (thinner) layer of paper masking tape. Once down to the thickness of the masking tape, the final 'ends' of the top panel could be finish sanded vertically with the side panels. Clamping the top veneer panel in position was a little more challenging. The top veneer was taped (masking tape) to a sheet of Teflon release paper, using the inner edges of the masking tape to mark the exact position for placement of the wooden case, and the rest of the tape to protect the edges of the veneer from glue ingress to the show surface. The amp case was prepared simply by protecting the show surfaces of the 2 ends with masking tape (the ends were already veneered and trimmed), and temporarily adding 2 wooden battens to help spread the clamping load. Both surfaces were then glued, and positioned using the masking tape edges (not being able to see the grain 'join' - this is where the measure of good luck came in !), before turning the case over and firmly 'rollering' the veneer to squeeze any remaining air out. The case with veneer & Teflon was then clamped as shown, using a spare 18mm kitchen cabinet shelf as a rigid back support, 4 quick release clamps holding the ends of the case to it, and the B&D work-mate to apply additonal clamping pressure in the middle.... remember, the top of the case had also 'warped' over the years, so needed the extra clamping pressure to hold it flat to the veneer.... Heath Robinson would have been proud ! |
23rd Jul 2018, 2:23 pm | #4 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
At this point, the main 3 veneer parts were on, trimmed to size, and ready for a final sanding, and finishing.
A few words to the Titebond Cold Press glue - I would highly recommend it. It appears to indeed resist 'bleed through' to the show surface of the paper backed veneer very well, as indeed advertised, and has more than enough open-pot time to apply it, even to quite large surfaces, and using only a small (2") foam paint roller to achieve an even spread. It dries well, to a medium brown readily sandable consistency, and seems to blend in well with the natural wood colouring - the next 2 photos below are 'end on', looking directly at the front edge glue lines (for scale, all the panels are ca. 3/8" plywood). The 2" foam paint roller worked well for spreading, and by wrapping the roller in cling-film directly after use (I also do the same when painting), the same foam roller could be used for all 3 veneer parts, over 4 - 5 days, wasting a lot less glue, and rollers. |
23rd Jul 2018, 2:37 pm | #5 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
The final three narrow strips (< 3/8" wide), intended for the front face edges of the case, were not needed - the original veneered surface, after sanding, appeared to be a good colour match to the new rosewood veneer, and narrow enough, that even with the glue lines the different wood grain structure was hardly noticeable (next 2 photos).
In the mean time, I've had a chance to 'finish' the amp case, as follows: # Sanded on all show surfaces - 240 grade paper. # Varnished (3 coats) with one component, solvent based, clear satin finish, yacht grade Polyurethane - with light 240 grade sanding after each coat, and white spirit wipe-down to remove dust (I ran out of 'tack rags'). I used the solvent base PU to get more 'build', and because, although it's clear, I slightly preferred the colour it gave. # Varnished (3 coats) with one component, water based, matt finish, Polyurethane (Wilko, clear, matt - as recommended by Steve) - flatting with 1200 wet & dry (wet), and a white spirit wipe-down, between coats. As Steve mentioned, brush marks & dust pickup seem to be much better with this varnish. # Wire wool (fine grade) 'polished' - photos below are at this stage, before the final polish. # Final step will be a good beeswax furniture polish (possibly with wire wool, if needed). With hindsight - I'd have paid FAR more attention to the wood grain 'wrap' around the corners, and clearly marked the exact positioning needed onto the back of the veneer, so it was at least visible during & after placing the (glued) veneers into position. As it happens, I got very lucky... Otherwise, I'd have to say, it's worked out much better than I'd expected - the last time I did any wood finishing to this standard was probably back in the '70's... so overall, well worth the time & effort, and thanks again to Steve, for the encouragement to have a go at it ! |
23rd Jul 2018, 3:37 pm | #6 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,865
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
WOW!! That looks stunning. Well done and thanks for the detailed write-up.
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23rd Jul 2018, 8:07 pm | #7 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
That looks super! Well done.
Andrew
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24th Jul 2018, 8:26 am | #8 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
I am amazed at the effort required to obtain such an excellent result.
This thread, and other links, has been so educational, I had never heard of « Hide « glue! Cheers John |
25th Jul 2018, 7:27 am | #9 |
Heptode
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 642
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
Impressive results!
Jac |
25th Jul 2018, 8:33 am | #10 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-Veneering a simple amp cover - a first attempt... (1)
Thanks guys - I must admit, I did enjoy the job.
I do still wonder how you could 'correct' warping on something like this ? Before refinishing obviously, but I couldn't think of anything short of completely dismantling it, steaming everything, and clamping each piece for an extended drying period - that seemed a bit excessive, even for me ! |