800B Chassis Install in 16A Cabinet

[Joseph W Strickland]

Over the last several days I have been working to get the 800B chassis to fit into my Metropolitan 16A cabinet. As part of the process I have moved the AM loop antenna somewhat forward inside the cabinet. It lies in the speaker enclosure part of the cabinet. There is only a very thin piece of plywood or Masonite on the back of the speaker enclosure area which will not be good for dealing with the planned bass reflex I will be creating in the cabinet. I have the speaker baffle board out of the cabinet for now. The grill cloth has to be replaced. It is badly faded and there is a dark stain in it around the circumference of the speaker opening. I will be looking for and ordering a suitable new replacement grill cloth. I will try to find something as close as possible to the OEM cloth, but so far I have not found anything that truly matches the design of the original cloth.

I need to add some wood cleats to the back of the speaker enclosure area in order to adequately secure and seal the back of that area with at least 5/8" plywood. Also, even the existing back cover had screw holes for the top edge of the cover just under the record changer compartment. Unfortunately there was no wood behind them to secure that edge from the time it was manufactured. I will put the OEM back cover in place after the new plywood piece has been installed so it will look like it originally did.

I had to re-fill some screw holes for the metal angle bracket I used in the radio tuner chassis area. one side somehow wound up lower than the other side. I used a depth gauge to discover this after sliding the door under the chassis caused a scuff mark along the low side. I may also add a thin soft felt strip to help prevent this before final assembly.

The completion is in sight now.

Joe

[Joseph W Strickland]

After many other activities, I finally got back to my 800B and the issues surrounding it being fit into a cabinet originally made for a Metropolitan 16A. At the last try a few weeks ago I discovered that the preset tuning assembly on the back of the 800B tuner chassis was going to strike about 3/16" into the bottom side of the cabinet top. I thought of using my router to route out that much material going forward about 3-4 inches. I was not eager to attempt that. I had been going over the issue for a couple of days trying to decide what to do. I happened to dream a possible solution - add 1/2" thick boards around the edges of the top and the middle supporting rib inside the cabinet to lift the entire top 1/2 inch which would put the top clear of the preset tuning assembly. I needed to check the cabinet to see how the top was attached. It was being held on with wood cleats and 9 #8 wood screws. I carefully removed all 9 screws and the top lifted off! I made a trip to a local Rockler store and bought some mahogany 1/2" thick boards and came home, cut and trimmed them. I laid the new boards against the top of the existing wood cleats, then marked the spots for each wood screw. I took the new boards and drilled pilot holes for the screws using a drill press.

Once the wood strips had been fitted and checked using new wood screws 1/2" longer than the original screws, I took time out to stain the edges of each wood strip and let that dry, then added clear lacquer to finish to a smooth sheen like the rest of the cabinet.

I installed the new wood strips letting the screw tips just penetrate about 1/8" above the top of each new wood strip. Then I laid the top on them and all the screws popped into the mating holes in the top. A little time spent tightening the screws all the way around resulted in the whole top being raised by 1/2" and allowing the tuner chassis to be inserted into the cabinet without any further interference.

I put the tuner chassis in place and laid its front wooden escutcheon panel in place and took some pictures. It has been a long process, but the end of the job is drawing near.

The arrows point to the added wood strips. The gray lines in the back edge of the top show how much material would have to be removed to get the preset tuning assembly to fit. I was afraid cutting a notch that deep would destroy the strength of the top and possibly cause separation of some of the wood boards which it was made from.

Here the radio tuner chassis is in position where it will be fastened in place. There will be some thin veneer added on either side of the front escutcheon panel to cover some areas on the interior walls of the cabinet that have some scratches and never had any stain or lacquer on them when the original Metropolitan 16A chassis was in the cabinet. When it is all finished it will be a neat installation with everything fitting properly and room to spare for removal of the chassis in case service is needed. The door will still slide under the tuner chassis as originally designed.

Joe

[Joseph W Strickland]

Here is a picture that shows the speaker grill and grill cloth. I had to replace the cloth due to stains on it. The metal grill was corroded on its front side. The back was clean and bright, so I turned it around. i repaired some splits in the wood strips that position and retain the speaker baffle board using some Elmer's wood glue first, then mounted the baffle board with its new grill cloth from AES. They had some cloth made for guitar speakers that was close to the original horizontal ribbed material, just a slightly different shade.

Joe

[Dave]

You got lucky with that top coming off clean, Joe. Have you completed the bass reflex speaker cabinet as yet ? Seem to recall you were to install self contained drivers and x-over.
Dave

[mike hadley]

Nice one Joe, that wood strip is almost invisible in the photo's, good project.
Mike

[Joseph W Strickland]

Dave;

Yes indeed. The cabinet makers really did me a favor by assembling it in the manner they did. The speaker is about to be moved to the cabinet. The bass reflex port will have to exit the back of the cabinet rather than the front. There just was not enough real estate on the front baffle board. I originally thought I would build a custom cabinet. When I found this cabinet on eBay, I knew I wanted it. It looks so nice and fits the styles available at the time. Even at $485 with shipping, it was far less than a custom cabinet would have cost.

I still need to do some work on the Garrard RC-88/4 record changer. The motor needs to be taken apart and the rotor shafts and bearing surfaces cleaned out, then new lubrication added. I already have installed a rebuilt drive pulley with one from thevoiceofmusic.com per Gary Stork. He also has many phonograph cartridges available that will fit older record changers of just about all brands.

I do have the diagonal corner braces for the back of the cabinet. They just have not been re-installed yet. Once I get all the cabinet issues at the front of the cabinet completed and the tuner chassis secured, the corner braces can be put back in place. The corner braces were also installed without any glue by the cabinet makers. The reason was that the tuner chassis of the Metropolitan 16A could not be installed with the corner braces in place. They had to be removed to do so. Viewing the cabinet from the back, the right hand corner brace for the tuner compartment even has a 90 degree notch cut into its diagonal side to allow extra space to get the tuner chassis positioned. The one on the left side absolutely has to be removed in order to get the 16A or the 800B tuner chassis to slide in or out.

Mike;

Thanks for the comments. It has been a slow process for the last year or so. Often it is best that I do not work on it every day. I have time to think things through. Sometimes I try various approaches before settling on the one to use in the repair or restoration. I will soon be working on the electrolytic can that you sent me. I plan to install a 16uF polypropylene metalized film capacitor in it which will be in parallel with an existing 4uF electrolytic underneath the chassis. I have already tried this and found that it eliminates residual hum coming from the power supply. It also raises the DC output voltage to the rest of the set until the voltage regulator takes over. I plan to add some in-rush varistors and may also add some series resistance in the output of the rectifier tubes so that the B+ falls back close to the original voltages. Alternatively I could add a bucking transformer on the AC input to the power transformer that handles the B+ and filaments. The mains voltage here at my house ranges from 119VAC to about 125VAC depending on the overall loads on the distribution line coming to my house. We are at the very last connection to the mains line. We often get power fluctuations that others on this line do not get. Our daughter's house next door usually does not get as many glitches as our house. We have to use a UPS on our television and audio equipment in the den/living room. We also have a standby generator rated at 12KW. It saves us from the frequent power outages experienced on a rural co-op power system.

Joe

[mike hadley]

Joe:

if you want any more cap cans there are plenty more available, the ones you have originated from a lift motor drive, that particular customer insists that all capacitors are changed at time of repair, including bus caps, it saves their company having to re-visit the site after installation, so there is quite often a large selection of "donor" cans,

an easy task to fine undamaged good ones.

My aw15 is still playing strong, there is a little hum when first switched on but goes after a 30 seconds or so, maybe the rectifier or possibly the two 3uf caps on the main chassis, I left these in because despite their age they check out ok, otherwise all is well, it will shake the floor with about 1/3 volume and a local station,

I'm really pleased with the speaker rebuild, the cone was missing and the voice coil damaged, but the history of this you know.

we used to have lots of trouble with our electricity supply quite often getting brown outs etc, then we had a 23 hour power cut, turned out to be our local sub station transformer burnt out, it was installed way back in the thirties when they electrified the uk.

Mike

[Joseph W Strickland]

Late yesterday I managed to mount the constructed coaxial speaker in the cabinet along with its cross-over network. The cross-over network is fastened to the bottom of the speaker compartment. Next step will be to add wood cleats at the back so that a cover can be fitted to seal the enclosure and add the tuning tube to the back. Here is a picture of the speaker in the cabinet.

The broad ribbon cable material is the AM loop antenna that came with the cabinet. The Metropolitan 16A used a 1:5 step-up transformer on the AM antenna input. I am wondering if that is what was used in the 800B models. In the case of the 800B there is an external matching transformer for the AM loop input. Has anyone looked at this aspect of the 800B and determined the ratio of the AM input transformer?

Joe

[Jon Ketron]

Joe,

Looks like your project is coming together well. Very nice!

Jon

[Joseph W Strickland]

Jon;

Yes, I am so glad that the end is now in sight. I will be cutting the board to seal in the back of the speaker area and adding the 4" diameter reflex port there since it could not be fitted to the front. I intend for the original thin board to still be placed over that which means I will have to cut two holes for the port.

In the meantime I am working on making a tube type stereo for my oldest granddaughter. She just graduated high school and loves good music. She has been buying LP albums lately of everything from big band to jazz and classical music. A number of young people now are going back to older analog equipment. She is getting a repurposed Fisher Electra pieced together from a model IV 440-A amp/pwr. supply and an Electra VI 490-T tuner. I had to provide a custom cable to mate the two different year two-chassis system, but it will be a good 17.5 watts per channel stereo in a custom equipment cabinet with changer and separate bookshelf speakers. I have some parts on order for it to get the power supply in good shape and change out coupling capacitors. The Electra VI has a nice eye-tube to indicate tuning and presence of stereo signal on FM.

Have fun!

Joe

[Jon Ketron]

Glad to hear Joe.  Your granddaughter will be pleased with the Fisher equipment.  Great to hear she likes big band.  I myself, a younger person of 28, enjoy listening to early Jazz up to the big band era of WWII.  Vinyl has somewhat made a comeback in recent years.

Looking forward to seeing the end result of your Scott project.

Jon