ABC electronics inc.250 plus w/pics

[johnny9]

well after talking to death some great members on this awesome forum i finally picked up a few boxes of radio stuff today..all i was after was the amp but couldnt turn down all the stuff so brought it all home..

the amp;abc 250 plus..looks to have a small tube driving a bigger tube,driving 3 bigger tubes..
i did some reading that these were good amps in the day.
when i opened it up a few min ago it looked way to clean for a almost 40 yr old amp,but the old man had everything in boxes so thats prob the reason.

everything looks ok..i assume these dark grey spots on the sides of the tubes is because there laying down and thats where the fan pushed the heat to on the tube? comments on this please?

i didnt clean it till after the pics and the transformer edges even came real clean,,yes i was very very carefull,,no zaps for me thanks,im a welder fab and been shocked enough in my life lol.

the fan runs super quite thankfully,and all the tubes lit up on standby similar to my tram except maybe a tad brighter..thats a good thing i guess.

well heres the pics of the amp and followed by my haul of parts for a buck fiddy..that was the amp included in this haul also.

i have a thread saved by captainkilowat and im thinking it should get me set straight on tuning it tomorrow.
im kinda worried about the old 110 plug with 2 prongs but i guess i can upgrade that after i get it up and going ..is that needed??

and any other help as to after plugging it into my tram with a 4 watt dead key then how to tune these 3 knobs PLEASE feel free to teach me what you can..
im a slow learner op:

edit;the old midland base radio sitting on the tram was part of the haul,the tram is not..just needed a place to set it.

if anyone may wants to no everything i picked up in them 3 boxes,heres a list.
on this page in this thread.
http://www.worldwidedx.com/general-cb-services-discussion/163025-any-no-amp-body-4.html#post455107

 

[johnny9]

how to tune a tube amp;by captainkilowat,,awesome easy to follow directions.
http://www.worldwidedx.com/amplifiers/26225-how-tune-tube-amp.html

i only have a problem with the first thing to do.
which is hook coax to dummy load?im a dummy lol?

does this mean i cant do this all hooked up to my antenna?
my astroplane reads very flat swr,s and never seems to change and ive used 3 diff meters to adjust and check them and there perfect.

need dummy load info for dummys ?

 

[johnny9]

well figured i would give a update..my tram had a cap start leaking so hooked amp to my mobile radio.
in another thread i posted the radio was deadkeying 10 or more watts but since then i changed back to the new meter"astatic pds2 10/100/1000 swr watt meter" and the radio is only keying 1.5-2 watts.
with the amp on it dosent key any more and when adjusting the tune or load it dont do anything different.
i feel the amp is working correct just another problem.
the amp relay clicks and keys up and all the tubes seem to be working,except one in the middle as its the only one that dont change when keyed up.
by change i mean the other 4 tubes when keyed kinda rev up and have a slight blue when keyed.but not the center one,it just stays lit and orange like the others when there not keyed up.

my tram d20,s drive tube gets blue when keyed also..i read this was a gassed tube and needed replaced..
but after talking to alan,the tube guy and he rebuils tube radios and amps/tv,s etc etc,he said that was fine and normal in some tubes and didnt mean it needed replaced..
my dad said the same thing,while i did read it needed replaced.
but im taking alans word for it as he works on them everyday since he was young he said..

so i feel the amp is working but no differenc when i key up to try to adjust it?
im thinkng the tube thats not changing at all when i key up,since in the center is causing the problem..I HOPE ANYHOW?
after trying to adjust it and keying up a few times i can slightly hear a crackiling noise but i "THINK" its the tubes getting hotter from being keyed up,then when i un key the fan is cooling them down?

really no clue just trying to figure it out lol..

any help would be appreciated as im poor since getting my daughter a 500.00 camera for xmas lol..among other things..goodnignt wwdx,im whooped,been cleaning the shack all day and got just a lil re arranged and done finally..:headbang

 

[johnny9]

another update;
swapped the center of the 3 6gj6a tubes for the one on the far end.

kinda was hoping the center tube i swapped to the end would do the same thing
it was doing in the center "not getting blueish when keyed"then id buy a tube.

but instead the same thing with the center spot.

im thinking the socket for the center tube has a problem or dirty connection but after removing them a couple times id think it would have connected.

all the tubes look great with no warped plates inside with magnified head gear but im no tube pro lol.

they all light up great just the center tube still dont glow like the rest when keyed up..well,i guess nobody can help figure this out so i will stop trying.

heres a pic of how purdy the old tube amps are.this should be a great amp when i figure it out..someday.

the second pic is while keyed up and all 5 tubes have a lil blue like i was told they should have..even tho you can only see the blue on the left one only they are all blueish except the center of the 3 in line..theres a smaller tube in the far right corner thats not in the pics, and it glows blue when keyd..

i was also told they were gassed and needed replaced when there blue when keyed so no idea what to belive,as all people that told me diff things are very knowledgable and service these amps??????????????????:bdh:

 

[fnkycoldmedina]

first off the dark circle on the tubes is normal ,its built into the tube .its called "the getter" .

the tubes appear to be burning ok in your pictures .far as output goes well no output means one thing pretty much ,bad tubes.

find someone with a tube tester to test them for you .

next thing ,be very careful playing around inside a tube amp .especially since i did not hear you say you drained the caps before going in . theres enough juice in there even when turned off to shock you very badly .people have died! been burned,shocked, you get the idea .

are you sure you have it hooked up correctly?it does look in good shape but that in itself doesnt mean it should work .

get the tubes tested,if they are low then you need to buy replacements,but some of the old sweep tubes might cost you more than the watts it will do are worth .
only you can justify the cost if its worth it to you or not .

does that tube in the center of the picture have a crack in it?or just a scratch in the glass? a cracked tube is no good right off the bat.

ps- make sure that the far right switch is in the "operate" position or it wont put out any watts .

 

[johnny9]

no cracks or anything..the tubes all look real good inside and out,not that that means anything.
they all turn slight blueish when keyed up except the center tube of the 3 in a row,,i swapped tube positions and still the same..
so if the blue is normal when keyed i guess i have a bad socket.
that sure seems to be the case as they all glow blue till i put them in the center socket,then no glow blue when keyed.

was told the blue meant they were gassed and read that as well.
but was also told by a couple guys that fix tube amps/radios that they were supposed to have a blueish when keyed up.meant there working?
so that kinda screws with me lol..
i will get it fixed either way as i want it to go with my d201 tram someday,but for now would be nice with the midland im using

 

[Johnnybgood]

Actually, there is more to an amp than the colour of the tubes. First of all from the pic you posted the fan is really only cooling the closest tube and the others are not getting much airflow. However, twith the amp closed up properly, the fan might cause a nice pressurized cabinet, enough to keep the tubes happy. I doubt it. On the under side of that amp I see some large capacitors which could well have reached the end of their life. The tubes require certain voltages in order to operate correctly. I would advise that you get the amp checked out with a circuit diagram. Some of those components underneath look a bit dody and with wires crisscrossing it is not a health enviroment at all. As someone else posted beware that tube amps can KILL, or at the very least give you a nasty shock and burn. If you dont know what you are doing, then DONT.

 

[johnny9]

i think i got it..i looked up getting the meter and connections correct and got it right and seen a diff immeadiatly..

i adjusted per captainkilowats thread and had good results.
i wasnt looking to talk and go big or nothing just trying to get started in the right direction so i can have it"properly in my mind" when everything else comes together when time comes.

now its on the side till i get antenna up another 20-25 ft.but "almost fully understand"

i got the tune and load adjusted to max smoke,then dipped the" load knob"a hair"advanced"..for poss better sound.will ask a few contacts when time comes.

also have the drive knob adjusted for max smoke as im not positive on the drive part yet.

the" load knob" is "plate load "correct? that i dipped a lil advance per captainkilawat thread?

so do the drive,tune and load stay adjusted to max power like i have it with the"load,,"dipped a lil like i read. then just use low and high when i want to talk?

sorry so long but wanna get it right for when the time comes to turn up the radio in the future,and re adjust amp.

 

[Johnnybgood]

One of the "problems" with a tube amp is that you will have to retune it again, if you move to far from the frequency where it was originally tuned up. You will see a drop in output power on your meter. Solid state amps dont have this problem as they are normally broadband...ie they are designed to operate over a wider range of frequencies. However they also have their limits as well. Tuning an amp for max smoke as you put it is really not on. what did the article say about backing off the load capacitor a a small bit and did you understand why its done?

Think of it as a automobile without a 5th gear. The 5th gear basically reduces the engine revs ( makes the engine run smoother, giving better fuel economy etc etc ) Running the valves flat ( max smoke ) out makes them run hotter, allows more splatter ( dirtier signal ) and will make them work harder, leading to a short life and more chance of something going wrong. Simple terms. Reducing the load load control a small bit does the opposite ...gives you a cleaner signal and allows the tubes to run just below the maximum design specs.

 

[johnny9]

yep,i think i understand much better than before.."DIP THE LOAD" makes sense.
if it were only as easy to me as engines id have no problems at all lol.

i put it as"max smoke"cause thats what ck said in the thread lol..the thread is linked in the first post or 2 in this thread but im sure youve read it..

kinda understand better with the guy below captaink,s post about his directions with tuning his pride 300 amp..

all my lights work on my amp and if i didnt have a meter i could do a fairly good job tuning with just the red modulation light.

the light really gets much brighter when your a the right spot of tune and load no doubt..

so help me understand the drive knob? it has to be tunes with the other 2 or it dont tune properly.
but when the tune and load are tuned can the drive be lessened for less power?
and not hurt the tune and load where they are set?? thanks for your time..

on a side note,when i was doing this tune up it was very fast on the keying up like 2 seconds or so as to not hurt anything.

also,the radio is set at 2 watts"maybe" so the amp was only putting out 80 watts on low and over 100 on high when tuned with this radio.
but at least iv learned better this go around,and when the antenna gets right and the radio more power,then the amp should do its thing as i read the amp needs 4-5 watts to get it running better

since the tram d201 was set aside and needs cpas installed im usining a midland 13-898b,and its like the bottom of the barrel compared to the tram.
maybe if i can figure how to turn the am power up it will improve,but it has no swing like the tram radio does..i feel the tram would be swinging over 400 with the amp<can not stand it>

 

[Johnnybgood]

If you reduce the drive ( radio power level ) then the amp will reduce its output. There is a set drive limit on amps and exceeding them is at your own peril, the same for the output. Lets say you have a 100w amp that needs 10w drive level to achieve this. More drive of say 15w will up the output level to say 140w, but the amp was not designed for these levels. The result is splatter, dirty signals, over heated components, and a short life of the tubes and the amp.

So if the spec says drive = 10w max, then stick to it. You will operating with a clean signal and people will recognize it and may well give you a clap or two ..LOL. Less drive = less output, but a healthier amp.

 

[johnny9]

ok thanks..so,if the amp needed 4 watts of drive,and my radio had 10,id use the drive knob on the amp after adjusting tune and load,to get the amp to the 4 watts w/out hurting it? that sound right.
and my 10 watt radio "dont have"could stay the same because i limited it with the amps drive knob? i think im getting it to sink in:w00t:

so when i adjust the tune and load,i also adjust the drive to get the amp working to the right level with the meter,,then leave the tune and load alone and adjust drive to not exceed the amps recomended input.

i dont have no specs or cant find any on this amp..only place i could find
Vintage tube type linear repair and build-it parts from Ken's Electronics, (Wholesale & Retail Electronic Parts) Kalamazoo, Michigan
has a schematic and manuel on it for 8 bucks i will be ordering,hopfully it has specs and tuning info also.

im just glad youve hung in there with me and help my slow comprehention mind understand better lol.
wiring and electronics is the very worst for me out of anything ive ever done.
i fabricate and weld ornamental alum and steel entry gates/hand rails all my life,and built a few engines,and love building jeeps and articulating 3 and 4 link suspentions to crawl over stuff..actually just built a 3 linked golf cart that really hauls butt lol..for a golf cart
thanks johnnyb
johnny9

time to search;how to tune and turn up midland 898b,and maybe get some kinda swing out of it,as it sure seems dead as he!!..wish there was a video somewhere for this stuff.

 

[Captain Kilowatt]

That "DRIVE" knob is likely not a level control but rather a driver tuning control. Adjust it for lowest SWR between the radio and the amp as read on the radio's SWR meter or external meter placed between the radio and the amp.

 

[johnny9]

so,my radio meter has perfect swr,s and the one inline near the amp reads a lil highr but under 2 swr,s.
so the drive will adjust the swr,s on the meter thats closest to the amp,and not affect the tune and load?
dang,if i got that right im actually came a long ways in my learning curve lol

if i could get a answer in the "siltronixs mod 90 vfo" thread i posted that would be sweet..but to others it prob a dumb question..but def a serious one:headbang

 

[wavrider]

Drive?? tunes the one tube "driver" into the three tube finals.



You have a two stage amplifier, the small tube is the keying tube.

I do not know if you have an input tune which would match the input of the driver stage to a decent VSWR, usually they are not in the smaller amplifiers and the input impedance is not very good.