What's Inside a Cable Line Amplifier?

[@sa8die]

i just started a job repairing these,. thanks!!

[@HillsWorkbench]

Depending on the brand, you may find a lot of vexing mechanical issues, like pad and Eq sockets or chassis with too much patina to ground to the housing well. Are you working on multiple brands or just one?

[@yz250ftony]

comsonics?

[@83jbbentley]

I work on the new C-Cor doing cap enhancements and changing out components. It’s pretty interesting work.

[@HillsWorkbench]

Warranty work?

[@Lano-cu2hp]

Josh. I stock all the components, send me an [e-mail]. my website. Www.chipstech.com

[@83jbbentley]

@@HillsWorkbench I know it’s been 4 years but it was if they damaged after hurricanes so I’d do assume as much. Sorry for the late response

[@yz250ftony]

missing 711mhz AGC(or sometimes 609, but usually in the 860/870). The moto AGCs get all twitchy when the can cap fails. Arris AGCs are reliable. The white coils on the diplex indicates 1ghz. the 860/870s are mixed black/white. GI hybrids are usually pretty good. Common to see a 20a fuse or shunt in these...they're only rated for 10 or 15a. The diplex typically aren't touched for tuning the slope, that's all in the MDR. The blue pot you pointed out is for the gain control. The white round pot to the lower right of it is for the AGC. The 3 white trim pots on the MDR fail quickly. The 1ghz units are finicky on grounding, especially on the standoffs to the cover.

[@ShaithMaster]

Looks like he didn't see that. I haven't really found grounding to be a problem on any Motorola or Arris minibridgers, only the ACI ones from Charter.

[@josephhuffer331]

@@ShaithMaster the MB100 have small grounding issues without the lid on

[@ftthponshenzhenchuangmo]

hi, Workbench, This is Candy Tan from China. we are experienced Hybrid module manufacturer in China. as NXP and NEC stopped production, if you need repair parts to replace NXP/NEC/PDI. can contact with us anytime. Thank you and best regards.

[@hullinstruments]

I’ve got a humble little electronics lab, and I enjoy repairing old test equipment. But I know nothing about RF nor am I interested in it. However I bought a literal truckload of these modules from my local electronica scrapyard recently. $0.10 per pound They are the newer ones, and I was curious if they would have any use for parts for non-RF applications? Like precision voltage regulators, or stuff like that? I’ve got all kinds of different modules… From smaller modules, some of the massive ones… And everything in between. Including dozens and dozens of plug-ins. Thanks for the video and thanks for your time!

[@hullinstruments]

It’s all scientific Atlanta stuff by the way. I assume that’s what you were meaning when you were quoting “SA” in your video

[@HillsWorkbench]

Yeah, for basic electronics use you'd pretty much focus on the switch-mode power supply parts. Good for playing with but I wouldn't reuse the capacitors for repairs or the like, understand that those modules have roasted in hell for several summers likely. You may be able to resell the hybrids and any EQ cards if of recent vintage.

[@toomanytums]

Oh God, you have a Magnavox. lol pretty old deal right there my man. The Motorola you have isn't uncommon though(looks like it could be an MB100 series,based on the # on hybrids which indicate a 1Ghz hybrid but could also be used as an 870Mhz). I work on the exact model you have there all the time as well as literally every other model from Motorola/General Instrument, CCOR, Scientific Atlanta, Broadband International, Aurora, you name it. Power supplies, Line extenders, multi-outs, nodes and housings. Very fun stuff in my opinion, particularly SM stuff :)

[@HillsWorkbench]

Yes, a relic of some bygone rebuild. But interesting to see how things changed. In more recent years I worked Motorola, Augat, old Tek-Scan/ Antec, and the Magnavox line that C-Core bought up and improved in terms of test ports and sweep. The switch mode power supplies of that line were the best, made them reliable. Augat swept the best but would occasionally burst into flames.

[@josephhuffer331]

Where do you work? Lol not many big repair companies

[@TheHotshots1]

I found a Jerrold Line extender JLX-7-750P/1C Laying in the middle of the road. Must have fallen off something and landed on the road. The case is bent a little but all the electronics look undamaged. Is it worth anything? Can any of the parts be used by someone who works on these?

[@HillsWorkbench]

It probably fell off a cable TV truck. It would be useful to someone who works with or repairs such but that is a pretty narrow sector. Probably removed to be repaired. Give it to a cable guy.

[@TheHotshots1]

@@HillsWorkbench Thanks.

[@witling]

Looking at the circuit board I expected what you called the ‘bump boards’ were the diplex filters. Where are the diplex filters?

[@HillsWorkbench]

No, don't think so, though if you gave me a time I could tell you for sure. The circuit components of diplex filters on Line Extenders and Distribution Amps are generally purposefully not accessible, they don't want users trying to tweak these. Bump boards are just the opposite, they are accessible so users can correct for slight bumps or dips in response. In practice even bump boards are best left untouched. It is folly to try to correct a little dip in response in the plant at an amp because as soon as temperature changes, so does the notch frequency and now the comp someone did in the amp is another fault.

[@haploideallel]

Please do go on with these explanations; even when there's jargon about. It is really interesting matter (imo)! :D If the terminology gets complicated, there's always wikipedia and/or the comment section to ask for clarification. Also, there's not much on youtube about this specific part of the world of hf-electronics. I think you fill a gap/niche that needs to be adressed ;) Myself being not an electronics literate (just yer basic Ohm's law and such), i still find me gaining knowledge and understanding about this subject matter (albeit just 'somewhat' though). Thank you for the elaborating so far already; really enjoyable and educational! :) (excuse my childish use of English; for it is not my first language)

[@HillsWorkbench]

Thanks for the feedback, I will do a few more on broadband cable networks.

[@jatlifevlogs2725]

Very interesting again. I'd certainly like to hear about the cable modems. Also about the power supplies for the cable system. Is power fed into the system only at the main office? What about surge suppression and how often used in the system?

[@HillsWorkbench]

Power is another very involved sub-topic, and there are a few surprises. It is a network of its own and doesn't always follow the (forward) signal path. A good topic though a lot to it.

[@leezy7787]

They're fed by power supply modems hooked up to a power meter and backed up by 12v batteries. Then signal comes from fiber optic into a node and then out to all the Amps and line extenders. I think?

[@YouTubeSupportTeams]

I have seen these deliberately left open, i.e the cover is on but not closed completely to allow heat out on a problematic DP?.. surely that would allow noise ingress??

[@HillsWorkbench]

Sorry, late reply. Yes, that would allow for more leakage/ signal ingress, but moisture would be the big killer. The problem typically happens when a tech thinks he will be coming right back, but gets called off to a bigger crisis elsewhere and forgets. We made it an informal rule to always close up even if you intend to be right back...

[@leezy7787]

Nice dude!

[@leezy7787]

I'm about a year into splicing osp coax for Comcast and love your vids, just subscribed!

[@jimholland6575]

How are the line amps powered?

[@HillsWorkbench]

I talk a little about it at 5:06. And more at 15:20. And a whole other video on how things are powered in a CATV network. kzbin.info/www/bejne/oWrHgnSLiKqJebc AC power rides the center conductor at 60 or 90 VRMS depending on the system. Basically there are three signals flowing in a CATV network, forward, return, and power. Power doesn't always come from the input, it can come from the output depending on power supply location. Power can also be stopped or allowed to flow through.

[@jimholland6575]

Thanks for posting the video and answering my question. Your video on power supplies for the distribution system was informative as well. I used to do volunteer work at a local CATV station at the local access channel. I would take a peek at the modulator rack tucked away in a small room now and then. It sparked my curiosity about how the whole system worked

[@teddyblair3922]

What MSO do you work for?

[@HillsWorkbench]

I took an early retirement deal from Comcast, so now unemployed, hopefully I can stay retired and tend to more creative pursuits. After being Chief Engineer for a private cable Co. for seven years, in '88 I took a job with Continental CC, then briefly we were part of AT&T, then Media One, and finally bought by Comcast. About a decade ago I took a linear transfer across my state to be closer to my "up North" place. My coworkers in this town went through even more ownership changes than I had.

[@teddyblair3922]

Sounds like my career.. Spent 26yrs in cable. Eleven year's with Comcast as a CT-5. Was retired in 2010 due to a disability. I worked for five different MSO's during my 26 yrs.

[@EmpathZ313]

Can we cut out the small talk and get to the point PLEASE