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Marantz 4400 no lights.....?

anderslober

anderslober

Yikes...not again!
I have recapped the PS and amplifiers ONLY. I tried a DBT test...all was good ...bright then dim......I then connected to normal power......no lights of any kind.
What gives? Aren't the dial lights driven directly of the tranny? The dial lights are new LED's.....................can they be turned ON by the tranny?
 
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HA....AHA!....bk...it was the lights fuse......sitting loose in its cradle....I fixed it and the lights are now running.

The scope works....but, it is very dim...even with the rear brightness pot at max. I also seem to get only a diagonal line......any ideas on what to test on the scope? I know the voltages are high..................
 
I am trying to tune the scope a bit. I have 192v going in on pin j907.......after r915 I have 86v........it should be 112v.............
The collectors of h905/907 measure 86v.............should be 112v......could this be my problem?
All other voltages are good. I measured the DGS on the FETs' too.......all good.

R925 has -278v.............going to pin j913....is this ok?
 
The brightness pot controls the 500+v feed for brightness, you getting 500 v to the grid of the tube, I believe it is G1. If you are getting 550v at max brightness the tube is shot.
 
What should the voltage be at max brightness?

Bk..did you see the other voltages? 86v seems a bit low.........is the resistor r915 out of spec?
 
R915 and the associated circuit will vary according to where the horizontal/vertical is set- when you adjust you should see it swing from a lower voltage to a higher one.
I believe at max it's around 570v.
 
HUH?.........it starts with about 200v on pin j907.......goes through r915....86v......am I reading it wrong?
The 570v stuff is the 'other' side of the scat'.........for the tube....
 
Dark room...here is what my scope looks like: Brightness is at 75-80%...no real difference from 100%............
 

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Did you measure the voltage coming off of J911? What I am saying is that depending on where the H and V are set, the voltage at R915 will vary- so long as the scope will center and display stereo all is good- this has nothing to do with brightness of the tube. Take the voltage reading at J911. In normal daylight a good tube will be as bright as an oscope- that looks pretty dim. If the voltage for the brightness is sitting at the -550v mark then the tube is on it's way out- 2bp1 substitute time unless you can find a hitachi original. R915 is the resistor at horizontal adjustment, when measuring if you move the horizontal pot you should see the voltage go high and low with the tuning of the pot. IF it doesn't then you have an issue with the transistors.
 
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How the heck would you wire up a 2bp1? Is that a simple operation?
I will measure the voltages where you say................
 
Bad news....j911......rear brightness pot all the way down .....559v..............bummer......anything else to check?
 
Nope- it's a CRT, pretty simple to diagnose, I went through this with Vintageplus' unit. Had -550v and dim- new 2bp1 tube , bright as a Christmas tree!
 
bk.....I tried adjusting the pots while looking at the voltage on the collectors.....I was able to adjust the voltage, so the transistors are good.
Excellent thread on the 2bp1 install.........I'll have a go at it!
I guess its just the tube then......................
 
Yup, it's the tube, sad but true. When Vintageplus' showed up it was the same thing, dim in the dark- after testing voltages I came to the conclusion that the Hitachi tube was shot, subbed in the 2bp1 which is literally a 30 minute job and it was cured. Nice to know there is an alternative, the OP of that other post was great to share that with us. I'm guessing this applies to the tuner and 2500/2600 that share the same tube.
 
How come I only get a 'monophonic' scope display? Even when playing stereo. I just have a diagonal line like on page 18, figure 18 in the UM. Shouldn't the scope 'dance' around a bit more with a stereo signal?
 
Bk...I am going to buy a 2bp1......will any model do? There are a couple different manufacturers..............are all 2bp1's the same?
 
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