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Another 813 Build




 
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Patrick J. / KD5OEI
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« Reply #50 on: February 07, 2019, 11:31:01 PM »

Wasn't there a picture of the power supply of this, like a short rack with a quite large size power transformer sitting in front of it?
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« Reply #51 on: February 08, 2019, 10:54:01 AM »

I've got that power supply in my shop.  Knocked me with 6kv.
--Shane
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How are you now BTW? I hope healed up well!!

I'm back working in the shop.  Cost me about 6 weeks of downtime but better than the alternative!  Dirt nap!

Glad you got the transformers.  Those oil caps, not sure I'd ever use them so figured I'd send them to someone who may.  And I still have a bunch left over!

If your asking me about the short rack power supply, no.  That was a different supply I built for someone.

The amp / supply that got me was built by someone else.  Incidentally, I've received another amp with a Killen connector.  Same problem.  Wire abraded going into the connector.  Idiots.

--Shane
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* 15496407115014967706118296981231.jpg (3948.5 KB, 4160x3120 - viewed 164 times.)
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w9jsw
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« Reply #52 on: February 08, 2019, 07:24:19 PM »

While I wait for the last relays to show up, I am going to knock out a pcb for the driver. Was never able to get hold of the guy that did the last one. Should not be too hard.

John
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« Reply #53 on: February 09, 2019, 11:28:43 AM »

Separate thread for the Mosfet driver board. I am laying out a new PCB.

http://amfone.net/Amforum/index.php?topic=44619.0

John
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« Reply #54 on: February 10, 2019, 01:45:45 AM »

I've got that power supply in my shop.  Knocked me with 6kv.
--Shane
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How are you now BTW? I hope healed up well!!

I'm back working in the shop.  Cost me about 6 weeks of downtime but better than the alternative!  Dirt nap!

Glad you got the transformers.  Those oil caps, not sure I'd ever use them so figured I'd send them to someone who may.  And I still have a bunch left over!

If your asking me about the short rack power supply, no.  That was a different supply I built for someone.

The amp / supply that got me was built by someone else.  Incidentally, I've received another amp with a Killen connector.  Same problem.  Wire abraded going into the connector.  Idiots.

--Shane
KD6VXI

OK, I just thought that I might have the same transformer as in front of the short rack power supply, and wondered if it was used with a bridge. IIRC mine has three big ceramic terminals on the HV side and lightly stamped '5800' but I have to check. (of course it is on the bottom shelf with the business end facing away, and it's too heavy to be moved easily..) Also wondering what the transformer is from. I guess I should post a picture of it and ask in a separate topic, kinda mixed up as to where on here I saw it, thought it was in this 813 build topic but can't find it now.

Well as far as those connectors - if you insist on correcting that whenever found, future generations of people may live to thank you.
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« Reply #55 on: March 07, 2019, 10:00:47 PM »

I came across this old pic of my Plexiglas 4-1000A modulated by 833As.  I had this thing about  being able to view the insides cuz we soon forget what it looks like once in a steel cabinet.  It worked pretty well but got transformed into Fabio II, the latest 4X1 X 4X1s. (in pics #2 #3)

Notice everything is on wheels or a pedestal - and EZ slip off enclosures for acccessible servicing.

A good excuse to check up on the progress of John's latest 813 rig...

T


* 4-1000A X 833As.jpg (321.56 KB, 1280x960 - viewed 212 times.)

* DSCF0001.JPG (322.03 KB, 960x1280 - viewed 170 times.)

* DSCF0002.JPG (331.52 KB, 960x1280 - viewed 156 times.)
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #56 on: March 08, 2019, 06:40:11 AM »

Ordering a chassis along with the parts for the impending mosfet board arrival and going to start metal work layout on the rf deck. Have been conversing with Chuck to get the placement of the right angle turns and turns counters correct. My tank coil and band switch is huge so I plan to use a 17x17x4 chassis so I have plenty of room. I also picked up a La Pointe roller for the reverse Pi grid input. Now I need to find another multi-turn apparatus. Thinking of a vernier knob for this one. Needs to be smaller to fit right.

The buying never stops, it seems.

Where do I insert the grid bias in the filter? on the cold side of the roller? Where do I use a cap to block the DC - assume on the input to the reverse side and I should use a 500pf value? Do you perhaps have an example schematic?

Should I be planning on forced air flow into the chassis bottom and plan to make openings around the tube sockets to get air flowing up around the tubes?

John

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« Reply #57 on: March 08, 2019, 12:33:58 PM »

Hi John,

I'll describe the grid circuit and then you draw the schematic and we'll go from there...



There are three paths, all starting at the 813 grid pins:


1) 2K > .001 cap to gnd

2) 2.5mH > .001 cap to gnd.    From .001 cap hot to grid leak resistor ... other side of GL >  .001 cap to gnd.   Hot side of cap >   -75V reg bias.


3)  .01 cap series >  300 pf variable to gnd.  Hot of 300 pF > roller inductor in series.  Roller other end> 1200 pF variable  to gnd.   Hot of 1200 pF > .01 coupling cap.   Other end of coupling cap is RF input.


No need for neutralization because the G-P is only 0.25 pF per tube and the 2K> .001 to gnd lowers gain to stablize everything. Good layout will help further.   Many have run 813s without neut with success.


Air cooling: Several possibilities:  Use heat-proof glass latern chimneys with holes around the socket. Squirrel cage pressurized from back or top of chassis. -  Underneath air pressure cools fil seals and glass envelope on top.   If no chimneys, then holes alone will suffice, but top plate seal is not cooled well unless a muffin fan directs air down from top at center of tubes in addition to air flow at bottom to cool fil seals.


If you can locate the proper size chimneys on the web, it makes a HUGE difference in overall cooling. I did that here and the 813 tubes show their appreciation by losing their blush... :-)

T

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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #58 on: March 09, 2019, 09:24:31 AM »

I think I am 100% complete on the design, Tom. Check closely the latest grid changes.

I have incorporated all that I can think of and all of the great ideas offered on this board. The project scope is huge but the benefits will be amazing... Think about where this started with a simple 1700v, 350ma supply and a single 8000 modded by a pair of 811's. Quite a difference!

Items to note on this revision -

1. New Grid input circuit with no neutralization planned - will build it very tight and shielded from the output tank. Floating roller inductor (found a nice one!)
2. Mosfet board interconnect added with NFB tap
3. Separate control of Mod and RF CT's
4. Switchable RX only antenna - going to try a LOG on 160M - http://www.kk5jy.net/LoG/
5. Arduino sequencer board - 6 steps planned (need to design this)
6. Safe start PS input - will shut down automatically if the power blips
7. Frequent use of Russian SPDT Vac Relays (They look like Plankton from Sponge Bob Cartoon!)
8. Spark gaps (will need to finalize a design and placement)
9. Changed to use the Gates dual 10V filament transformer.

I have all of the parts except the chassis and relays. I think I am finally ready to start! (measure twice - cut once analogy appropriate here)

Paper is easier to change than metal.

My PS will be started later. I am still mulling over the final enclosure. The rack that I might get from work only allows a 17in by 17in space. That is not enough space to cram all of that Gates iron into it without a lot of KY Jelly. I don't want to cram it in and have arching issues if a darn spider decides to make a web inside. A Gates enclosure is quite spacious in comparison.

I am going to start on the RF deck first. It will be on a 17x17x4 hammond chassis with I think a 10U front panel, with right angle drives underneath to the turns counters. The vac caps will be mounted vertically on either side of the chassis. Two tubes up front, with chimneys. Large Tank Band Switch and inductor behind the 2 tubes with the switch rod running between the tubes. Input tank vernier and knobs below.

Face will have meters across the top, tube viewing oval holes with the TBS knob in between. With chimneys, may skip the holes since the tubes will not glow much. Input tank controls south of the BS in the center, Plate and load outside on the same axis as the input tank.

I think that is it! Any comments or suggestions will be readily accepted.

John

* 813 Transmitter.pdf (185.26 KB - downloaded 75 times.)
* PCB_DRIVER-PCB.pdf (41.11 KB - downloaded 65 times.)
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« Reply #59 on: March 09, 2019, 10:34:22 AM »

Looks good, John...

Just a couple questions regarding your schematic....

The plate current meter in the 813 Final cathode (filament) circuit will read combined plate, screen, and grid current.  You may want to consider floating the positive return of the control grid supply, as well as the negative side of the screen supply, and returning them to the center tap of the filament transformer.  Alternatively, you may float the negative side of the high-voltage supply, and place the meter between the supply and ground such that the 1000 mA meter reads only plate current.

You might also consider a higher voltage rating for the blocking cap coupling the plate circuit to the output tank.  5KV seems a bit marginal.  I use a pair of Sprague 20DKT5 caps in parallel, 500 pF each at 20 KV.  One may be sufficient.  Consider the capacity in parallel with the output of your modulator and its effect (in addition to the plate supply bypass capacitor)  shunting the higher audio frequencies when sizing this capacitor.

I do not see any protection for screens, should you lose plate voltage or excitation.  Perhaps some logic that requires drive and plate voltage before enabling the screen supply, or maybe a clamp circuit?  If screen supply is present without plate supply, the 813s will be very short lived..  GL on your project.
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« Reply #60 on: March 09, 2019, 12:13:08 PM »

John,


Hey cool.... this is my post 7777.   Lucky mega-jackpot!  Where do I pick up the cash?
Grin

OK on all. That rig is certainly turning into a professional project!   Now if you can maintain the workmanship at the same high level, you will be in the rare category of having a rig worth MORE than you spent on it...   Unfortunately, our time is usually way below minimum wage.  Wink

As Rick said, there's no screen protection. The modulators are OK since they are triode connected, but the RF finals will be at risk. Some guys chance it and are careful, but I prefer SOME kind of scheme to protect us from dumb mistakes.  In my 4X1 rig, I used robotics industry magnetic sensors that could be adjusted for current to trip a latching relay that opens the PTT circuit.  The shutdown delay speed is not as important with tubes as it is with solid state. Tubes can take more abuse for a second longer, usually, so mechanical relays are OK.   SS devices are milliseconds or less to damage.  

I used these magnetic current sensors in series with each DC circuit for the plate, screen and grid circuits for both of the RF finals and tetrode modulator tubes. So now if one of these tube elements goes past my preset limits, the PTT circuit opens up. (the fil CT opens so no current will flow thru the tube at all) It's kinda slick. I could come in drunk, turn on the rig and not blow things up... Grin   Do a search for current sensors and see what you find. It's easy enough to design using the sensor and a latching relay which opens up the 24V keying PTT circuit with a set of contacts.

The screen clamper circuit will work FB too.  Yes, 5KV for the plate coupler cap is a little low. Go for 10KV or more.

Your grid input circuit looks OK on the new schematic.

BTW, you don't have to use a tube, VR75, for fixed bias grid reg. A SS 70-80V  10W+  zener will work too.  This regulated voltage is to keep the grid bias filter cap from charging/ creeping up due to RF rectification. When testing, be sure this fixed bias stays solid with a full RF carrier. If it rises, I have a simple two component fix if needed.


When using the 813 chimneys, the drilled chassis holes around the socket base increase the chimney airflow.  Another way is to use spacers to make a gap so that there is 1/8"-1/4" recess of the sockets. This way no drilled holes are needed and the gap lets the air thru. The tube is designed for no pressurized air required so anything you do is a bonus to cooling effciency. As long as some air passes by the fil seals you are OK.

You can monitor plate current either by mentally subtracting the grids and screen current (as I usually do) or do as Rick suggests and float things.  The plate current meter in the negative lead is FB too. It's all up to you.

I'll look closer at the schematic later, but I think you are getting close to a workable build soon. The others here will hopefully see some more improvements or mods to make.

***  The mod reactor cap (C1) should be more than 3KV. If you can find another cap, put it in series for 1 uF @ 6KV.


T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #61 on: March 09, 2019, 12:44:23 PM »

John, here is an example schematic (from Jun 56 QST) that shows how easy it is to place the plate current meter in the negative supply return instead of between the final cathode (filament) and ground....  All of course better than the old way of putting it in the positive plate supply lead - (ouch).  The 5 to 10 ohm 50 watt resistor ensures the negative supply connection is not broken, even if the meter is disconnected or fails.  The resistance is high enough that it will not significantly affect the meter reading, even though it is in parallel with the meter.

It also shows properly-sized caps for the plate coupling and bypass.  Hope this is helpful to you.


* AmpJun56.JPG (77.18 KB, 874x515 - viewed 172 times.)
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« Reply #62 on: March 09, 2019, 05:11:17 PM »

I'll add, always but ALWAYS use a couple to a few 6A10 or 10A10 diodes from b- to ground.

They will clamp if that resistor opens up, preventing the chassis on the rf deck from approaching b+ value.

With a 400A surge rating they will take a lot more current than the meter and / or a 50 Watt resistor.

I size mine so the V Drop across them is the same as what is needed for plate current, then add one or two more to ensure they do not effect the plate current reading.

If you use inky enough diodes to pass said voltage, you start having the diodes conduct and pass current effecting the meter.

Try it on a small variable supply.  Two diodes in series will start passing current before 1.2 volts.

I've had to throw a LOT in series to repair / safe off others amps.  I had a 500Z amp come through here with all beautifully matches Simpson meters.  Except the HV plate current meter was in the b+ lead, causing 4kv to be present between the meter internals and ground!

Moved the meter to the b- side.  Took 11 diodes in series to prevent any diode clamp action effecting said plate current reading.  BUT if that meter opened up, their will only be 7 or so volts from ground to rf deck.

--Shane
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« Reply #63 on: March 09, 2019, 05:26:47 PM »

It appears that a meter in the HV- lead will read both PA and modulator plate currents on the common supply as John has.

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« Reply #64 on: March 10, 2019, 08:59:15 AM »

ok on the higher voltage ratings. I actually have 20K and 30K doorknobs as well as some ruskie doorknobs that are 30K. I will update the schematic. Tell me more about the audio passthru. I have 4 500pf's and 2 470pf's to choose from.

The reactor cap is marked 3kv but it is the actual cap that came out of the gates so my guess is that is the working DC voltage not the peak. However,  that is the only component that I now have from the Gates that seems marginal in rating, so I will do as you say and add a twin. Safer approach than trusting an engineer's decision back when I was born (mid-50's). I have more risk than he does if it blows, I am sure!

On the screen, have doubled the plate relay to also turn on the screen. If HV happens to be present with the screen and plate off, what can happen?

We need to discuss the metering better. I understand all that was said but agree that putting it in the HV- will now read both plate and mod. The bigger issue is that changing the bleeder configuration breaks my compatibility with using the HV supply with my L4B. If I am going to add this I need to do it on the RF board only. Thinking.

I floated the screen and bias returns.

I have to rewire the filament supply feed from the controller. I have not looked yet but am sure the Gates fil trans will be 240V. Also, may need to buck it or add a variac to get it to exactly 10V. Going to add a filament voltage meter.

With all the relays and the variacs, I think am building Dr. Frankenstein's lab... Sparks a'flying and relays a'clacking!!!

John

* 813 Transmitter.pdf (187.87 KB - downloaded 52 times.)
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« Reply #65 on: March 10, 2019, 12:57:36 PM »

It appears that a meter in the HV- lead will read both PA and modulator plate currents on the common supply as John has.


Steve,
Yes, you are correct. Good observation.


I think John now has the metering all independent in his latest schematic by floating the negative for the grid and screen supplies  - and then keeping the plate current meters in the fil CT leads for the plate mod and plate RF.  That should all work FB now unless I am missing something. For each solution there seems to be a disadvantage but this is a good compromise now.


John, what do you mean by "audio passthru" caps?  Maybe you mean limiting the plate bypass and plate coupling caps to 500 pF max so that the extreme audio highs are not shunted too much.  Then yes, keep them 500 pF or so. Remember that the pi network has 1300++ pF to ground at times and that plate coupling cap is the only isolation from this being part of the mod xfmr audio circuit.  The smaller the better, as long as it works OK for RF..


Your question:   "On the screen, have doubled the plate relay to also turn on the screen. If HV happens to be present with the screen and plate off, what can happen? "

HV and plate are the same thing to me, so not sure what you mean.  But if the HV is on the tube, PTT keyed or not keyed in the fil CT, fil voltage on or off, screen off, then no problem.    The only problem is when there is screen voltage on, fil voltage on, PTT keyed, HV off.  This will cause excessive screen current and do damage.   We should probably make up a matrix table showing various voltages on or off, PTT keyed or off, fil voltage on/off to show all of the possibilities. But once you sit down and think it out, you will have a better understanding of the risks and what you should not do.


But the risk still remains... even if you have sequenced screen voltage keying, what happens if you are transmitting and the plate supply fails for whatever reason? Your screen current will soar and possibly do damage to the tubes before you are aware enough to unkey the PTT. That's why a current sensor or clamp is required in the screen circuit.  Accidents can happen to the grid circuit too but to a lessor degree.  

Once you get the rig running, you can carefully try different scenarios and see just what you can get away with and not.  IE, key the PTT, slowly add a tiny amount of screen voltage with the Variac and apply a small amount of drive... Turn on HV and see what happens, etc.

All of this is akin to driving a dragster. There is nothing automatic and safe about any of it. There's a lot of knobs and adjustments and easy to get into trouble when trying to make them all work together smoothly.

You continue to do a fantastic job putting this all together, John!!

Did I cover everything for now?

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #66 on: March 10, 2019, 04:18:03 PM »

ok, Tom, great explanation. So screen is not an issue unless the plate disappears, right? Then the screen becomes the plate and bad stuff happens quickly. So I really don't need to key the screen. Just have a clamp on it that activates if I lose HV, right? Is it that simple?

John
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« Reply #67 on: March 10, 2019, 05:06:03 PM »

John,

Yes, this is correct.

Essentially, if the HV and screen are both always on, or get sequencer turned on or get turned on together, no current will flow anywhere until the fil CT is grounded with the PTT relay contacts.

So everything will work FB until you lose the plate voltage by accident while the PTT is on.  Then the screen magnetic current sensor or screen clamp circuit takes over.  The sensor will break the PTT control line so that everything sequence cycles off.  You COULD also have a direct path from the magnetic current sensor to the screen DC circuit to break it so it occurs faster, outside of the PTT sequencer rotation.  

Or an all-electronic screen clamp shutdown circuit would be the fastest of all.

There's many options here.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #68 on: March 10, 2019, 09:47:43 PM »

I get it. I am planning to use the Arduino for sequencing. It can also read some current sensors and convert it from A to D. I can have set points that then override the sequencer to drop the whole shebang in an orderly fashion. This could be pretty cool.  Cool

I think I may even have to find some room for a 4 Line LCD display. My DDS is already being run by an Arduino and has a Freq display.

John
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« Reply #69 on: March 10, 2019, 10:55:43 PM »

Sounds slick, John!

When I have a fault in any of my six current sensors, hearing the sequencer cycle down in an orderly fashion is a thrill.  I use latched LEDs to identify which tube element caused the problem and a master reset button to try it again.


I have a question for the group related to the screen clamper, etc.  

**Update:  Never mind - question answered offline.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #70 on: March 17, 2019, 10:44:45 AM »

Chassis on order.

What is a good rule of thumb on how deep to make the decks to fit in a standard rack? The Motorola rack I had my eye on is just too small. Only 17in deep. I really need to make the PS and the Mod deck around 17in x 20in or so. The mod deck will have a 17x10 front chassis for the tubes and mosfet driver. It will set on a wood platform that has space in back for the mod transformer, mod reactor and reactor caps. I think I can get them to fit in 10in of space or maybe a bit more. The PS is needing a wood platform of about the same 17x20 or so. A few more inches would be even better. How about 17x24in?

Looks like the Lehman FLG globe will work for the chimney unless anyone can suggest a different one. How do you attach them to the chassis? Price is now up to $6.95, not too bad.

John
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« Reply #71 on: March 17, 2019, 12:59:15 PM »

Hi John,

The boards arrived and are beautiful - thanks!

Here's the link to the "813" chimneys for the other guys. They look like the ones I used. Great price for temperature-rated glass. They can be secured to the chassis like chimneys made for 3-500Zs, etc. Some kind of clips that have spring.  Three or four clips in a circle will do.  Look around and you will find something that will work, even if they are the expensive Eimac clips. Put your blower motors on a Variac and you can set the air flow to a very quiet level but still cool FB.

If you sub-mount the 813 tube sockets by 1/4" or so, you will have a good breeze thru the chimneys. No need for air holes in the chassis.

https://www.lehmans.com/product/clear-globes-for-dietz-blizzard-lanterns

As for the cabinet depth, that really depends on what you can find. I have always been very grateful when I find a DEEP cabinet. The extra depth always gets used.  Even if not, the extra room for working and better ventilation is FB. Very few hams ever complain about having extra space in any situation... Grin  My cabinet for Dr. Love is 30" deep. Even 36" would be FB.

T

Dr. Love:  Notice the trap door when I used plug-in coils. Dr. Love now has a big bandswitch.  Look closely and notice the fiberglas air ducting for the cooling outside. That has since been chaged to a sub-chassis blower with a Variac.

My all-time favorite color combination has been a white panel, black lettering, with a "blue IBM"  cabinet.  

Below: The days of wine and roses... and sweet memories.


* Dr. Love 30 inch deep cabinet.jpg (317.87 KB, 960x1280 - viewed 120 times.)

* YAZ SAILING.jpg (328.53 KB, 1280x960 - viewed 95 times.)

* Yaz kayaking 2.jpg (87.14 KB, 960x720 - viewed 144 times.)
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #72 on: March 17, 2019, 03:20:41 PM »

John,

Since you're still on the quest for a rack....

It makes a big difference in accessibility by having the rack side panels easily removeable. This includes the rear door, if any.  You can actually lean in and work on the rig when the side panels are removed.  Some racks do not have removable side panels, so be sure.

Also, be sure to have a bracket or shelf that supports the bottom of each rack panel. Most racks have brackets and/or mounting holes to start the process.  Holding the chasis up by only the 19" rack screws is NG. You will be axing the XYL for help unless you are Dick the Bruiser.

Better yet, if you are really smart, get some of those 19" rack slide in/out assemblies that lets you work on each 19" unit out in front of the rack.  Just be sure you have plenty of weight in the bottom of the rack or low enough C.G. to prevent rack tipping.

Make sure the wheels are extra heavy duty AND the wheel brackets holding them to the rack are extra strong and well reinforced. I actually had a rack NEARLY fall over in the shack when one of the front wheel brackets collapsed.  I caught it in time and had to wrestle it into a safe position. The biggest stress is when you are moving the rack over uneven or rough floor, rugs, etc..

Be sure the height fits into a room with low ceilings... or lower ceilings in the future.  (crystal ball)

Paint it to perfection as soon as possible, before you start putting stuff in. Otherwise it may never get done.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #73 on: March 17, 2019, 03:37:52 PM »

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John,

Since you're still on the quest for a rack....

Me too! I wuz doing that in WallyWorld today and almost got thrown out for gawking??
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« Reply #74 on: March 17, 2019, 03:48:17 PM »

Quote
John,

Since you're still on the quest for a rack....

Me too! I wuz doing that in WallyWorld today and almost got thrown out for gawking??

always a wise guy in the crowd  Roll Eyes
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