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2226B glows on DBT

Mico

Mico

Well-Known Member
Just finished recapping amp and PS board, plus big filter caps on 2226B.
Everything went well and I tried it on dim bulb tester first - bang, it glows pale orange on 60W bulb :sigh:. DC offset is below 10mV on both channels,
bias is around 15mV so nothing wrong there. It sounds good on headphones
and after 10-15 min. nothing inside gets hot or even warm :scratch2:.
I did whole recapping thing in one shot but going slowly, cap by cap, checking for clean soldering paths and making sure no solder residue rolling around.
When run through DBT on 100W bulb, which is almost an open pipe considering 2226B`s max consumption of 130W, no glow and no fireworks - receiver works fine. Could it be safe to plug it to the wall outlet or I should check more for the cause?

Just for comparison, my 2238B makes 60W bulb filament barely visible and even on 40W glows less than 2226B on 60W.
 
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The lamp should get bright then dim. If it does this then it passed the test.



Barney
 
It glows brighter on 60 because the unit is trying to pull more current than the bulb can provide. Once you switch to 100 w the current is satified and therefore no more glow. You are good to go at full voltage. A short would make that bulb light up like dentists light. Remember that you dont have the volume up so all you are seeing is idle current.
 
bktheking said:
It glows brighter on 60 because the unit is trying to pull more current than the bulb can provide. Once you switch to 100 w the current is satified and therefore no more glow. You are good to go at full voltage. A short would make that bulb light up like dentists light. Remember that you dont have the volume up so all you are seeing is idle current.
Click to expand...

What worries me is that 2238B glows way less having identical idling power of 27W . Not really a dentist light but 2226B glows a bit too much for what I consider "dim". Yes, it lights up bright first and than goes down but not to total shut off to return to dim glow - just reduces intensity and stays there.
Once upon a time I had a receiver acting exactly the same - but it showed through high bias (150mV) on one channel and it turned out to be bad bias transistor.
No obvious signs here and I do not know where else to look.
 
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bktheking said:
Is the idle current spec the same between the two units? Something to consider.
Click to expand...

Took the chance and connected it to the wall outlet - nothing happened, worked great! Than let it run for 5min. and moved back to DBT with 60W bulb.
This time everything went by the book, first bright glow than bulb shuts down than goes back only to show bulb`s orange filament - exactly like 2238B does. Have no idea what happened, my only guess being that big caps were charging. I used 6.800uF/63V while originals were 6.800uF/40V , could not find closer match. Thanks everyone!
 
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