| Author |
Message |
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 2:11 pm Post subject: |
|
|
He we could put a LC combination in the emitter peaking of the hybrid. Making a bump at a certain fixed frequency? Making the Barco fixed resolution lets say 1080p@60.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
 |
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 3:56 pm Post subject: |
|
|
| Quote: | | If you want the motorola better buy some marquee neckboards at 25 euro. |
Im not sentimental, but killig a neckboard just for the transistors is some kind of crime...
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 4:05 pm Post subject: |
|
|
| the dude wrote: | | Quote: | | If you want the motorola better buy some marquee neckboards at 25 euro. |
Im not sentimental, but killig a neckboard just for the transistors is some kind of crime... |
 Better rework them to fit in the Barco.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
|
| Posted: Sat Feb 20, 2016 4:09 pm Post subject: |
|
|
| the dude wrote: | | Quote: | | If you want the motorola better buy some marquee neckboards at 25 euro. |
Im not sentimental, but killig a neckboard just for the transistors is some kind of crime... |
Umm... I'm just bought a few months back Curt's last four Marquee 9000 VIMs just because of the AD834s in them, otherwise they would have landed in the trash. Now if you want to buy an AD834 from a supplier it is 30USD / piece...
I'm also not sentimental but in these days more CRT projectors end up in landfill than you think, and even the low end ES machines incorporated carefull workmansip and engineering. So reusing the parts are still better than ending up in a landfill.
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 4:13 pm Post subject: |
|
|
That would be possible, but you have to add a g2 regulatur, a power supply and all the abl stuff.
Another idea: There is a gas discarge protector on the cathode, a CG2350L. It is already very low capatitance, the datasheet says < 1.5 pf. Maybe replacing it with something better or 2-3 protectors in series may increase bandwidth a little bit since the driver has to drive this capacity also. This has only very little improvement potential, but one add to the other...
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 4:25 pm Post subject: |
|
|
Another thing:
Assuming the cathode has 10pf, the RLC formed by R19 and L2 has 118 Mhz cutoff.
What is the reason for this filter? Prevent oscillations?
Maybe we should reduce R19! Is there anything bad that could happen like kill the amp by oscillations maybe?
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 4:33 pm Post subject: |
|
|
|
Maybe it would also be a good idea to add little inductors in series with R15, between the source of Q5 and the cathode drive and on emitter and base of Q2 in order to decouple it from HF. There is no high frequency during ABL, so this might help to reduce capacitive load.
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 4:39 pm Post subject: |
|
|
|
Forget Q5, i don't understand what it is for exactly, but it seems to a video bypass for the diodes.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 5:19 pm Post subject: |
|
|
And why is L1 C21 not mounted? Seems to counteract L2 with the tube?
Nice idea those inductors.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 5:31 pm Post subject: |
|
|
| the dude wrote: | Another thing:
Assuming the cathode has 10pf, the RLC formed by R19 and L2 has 118 Mhz cutoff.
What is the reason for this filter? Prevent oscillations?
Maybe we should reduce R19! Is there anything bad that could happen like kill the amp by oscillations maybe? |
I do not see any feedback coming from the tube so I am thinking there can not be oscillations? There is only dc feedback in the ABL loop.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 5:35 pm Post subject: |
|
|
Nobody knows.... Also R38 is ridiculous high.
Just testet emitter peaking on the hybid. To make it short: Forget about squeezing out even a single Mhz out of the driver. I peaked it until color bleeding happened with no improvements in the high frequency range. Just lower frequencys became more dominant.
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 5:36 pm Post subject: |
|
|
| Quote: | | I do not see any feedback coming from the tube |
HF is voodoo, there is always stray capatitance and feedback, and a simple wire is never a simple wire
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 5:53 pm Post subject: |
|
|
| the dude wrote: | | Quote: | | I do not see any feedback coming from the tube |
HF is voodoo, there is always stray capatitance and feedback, and a simple wire is never a simple wire |
Ok and I can imagine that for hf the tube capacitance is a very low impedance and perhaps the hybrid is running hot because of that useless hf short?
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 6:26 pm Post subject: |
|
|
| the dude wrote: | Nobody knows.... Also R38 is ridiculous high.
Just testet emitter peaking on the hybid. To make it short: Forget about squeezing out even a single Mhz out of the driver. I peaked it until color bleeding happened with no improvements in the high frequency range. Just lower frequencys became more dominant. |
Damn. Good you tested this. I dis sort of fear it. But strange that if we peak before the hybrid it does get better a little. Perhaps that L1 C21 is an option? It is mentioned as the second external peaking network. It is tuned to 37 MHz (mid freq) with the given vallues. But the R should be more than 0.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
Last edited by redfox001 on Sat Feb 20, 2016 6:51 pm; edited 3 times in total
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 6:31 pm Post subject: |
|
|
Also the diodes D3 D4 have a little capacitance. Are they really needed? Mike removes those diodes from the Marquee neckboards.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 6:59 pm Post subject: |
|
|
Straight to page 16
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 7:02 pm Post subject: |
|
|
| Quote: | | Mike removes those diodes from the Marquee neckboards |
Mike removes everything he does not understand 
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 20, 2016 7:06 pm Post subject: |
|
|
|
Ah, series peaking... OK.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 20, 2016 7:16 pm Post subject: |
|
|
| the dude wrote: | Another thing:
Assuming the cathode has 10pf, the RLC formed by R19 and L2 has 118 Mhz cutoff.
What is the reason for this filter? Prevent oscillations?
Maybe we should reduce R19! Is there anything bad that could happen like kill the amp by oscillations maybe? |
Just read that this is series peaking. At 118 MHz the impedance is 0. Might be tuned a bit lower to 80 MHz?
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
|
|
