Explorer 4240HDC Cable Box Auto-Tuning Behavior

Does this happen on all the receivers at the same time? Is the receiver powered on?

StephanieA said:
Does this happen on all the receivers at the same time? Is the receiver powered on?

The auto-tuning occurs on a random basis across the three boxes. For example, at 6:00 a.m. each box may be tuned to the same or a different channel. Box 1 may auto-tune to Ch. 1998 within 1-2 hours. Boxes 2 and 3 may auto-tune to that channel at different times later in the day. I've never seen two boxes simultaneously auto-tune; but I've occasionally observed that two or even all three are displaying Ch. 1998 at the same time after a lengthy period has passed without any current or scheduled channel switching on my part. As further illustration, say a recording on Ch. 200 (HBO) is scheduled to begin on Box 1 at 1:00 p.m. If Ch. 1998 is displaying at that time, the box will switch to Ch. 200, complete the recording, and continue to display Ch. 200. Sometime later, that box will auto-tune to Ch. 1998. Each receiver is set to always display the channel and is kept on 24/7. If a box powers off, for any reason, it is set to display Ch. 10 (PBS) when powered on again. Thanks for your assistance.

I'm showing your cable receivers are HD only receivers and that you have 2 cable cards on the account. You mentioned this happened during a recording. Is this occurring on your cable card devices?

StephanieA said:
I'm showing your cable receivers are HD only receivers and that you have 2 cable cards on the account. You mentioned this happened during a recording. Is this occurring on your cable card devices?

Auto-tuning to Ch. 1998 has never occurred during a recording. Your question regarding cable card devices stimulated further consideration of this issue. Please note the following: 1. The cable cards, along with tuning adapters, are connected to two Tivos. These cable box replacements are controlled by the Tivos and enable channel switching during program viewing and recording by using the built-in program guide. Since the Tivos don't connect to cable boxes, auto-tuning is unrelated to these cable card devices. 2. Each cable box connects to a Replaytv which controls the box via an IR blaster coded for the 4240HDC. The program guide on each Replaytv is able to switch channels on the box during program viewing and recording. This guide is updated daily by software using a Cox Digital lineup provided through an independent subscription service. I removed Ch. 1998 from that lineup, and it is no longer available as a channel listed in the program guide. Although this action has effectively eliminated the Replaytv as a factor, auto-tuning to Ch. 1998 continues to occur on each box.

I'm guessing this is a ReplayTV issue.  I can't be positive without further analysis but my replaytv will sometimes do something similar with my Motorola DCH3200 cable box.

I think it's a combination of issues.  The first issue is I think there is a timing bug in the the ReplayTV system when it sends long IR codes through the blaster.  Digits will sometimes but rarely get dropped.  This problem will usually only manifest itself with 4 digit channels.  I'm guessing this happens when the ReplayTV's interrupt loop gets too busy.  The only way to completely fix this is to not use 4 digit channels.  e.g. set HD auto tune in your cable box.

The other issue is incorrect IR timing delays from the ReplayTV to the cable box.  Again, you see this the most when the ReplayTV  needs to send 4 digit channels.  I think this is your above problem.  This can be solved adjusting the timing delays during ReplayTV IRcode selection under setup.  The erroneous 1998 channel change shows up when the replay sends it's wakeup signal to the cable box.

Again, these problems occur even though it appears that the replaytv controls the cable box perfectly when you manually test it.

Do your problems disappear if you stop using all 4 digit channels?

@Jole60, are you able to test the changes that Mark suggested? Please let us know the results!

@Mark_K, thanks very much for the information you provided!

Becky said:
@Jole60, are you able to test the changes that Mark suggested? Please let us know the results!

@Mark_K, thanks very much for the information you provided!

Becky, this is what I've done so far. Mark, your thoughtful insights are always helpful and appreciated. Regarding discussion of four-digit (HD) channel tuning, I have always removed HD channels ( Ch.1003+ on the box) from the ReplayTV program guide as soon as they appeared. This was done because ReplayTV is a SD device which cannot output a HD signal. Since the auto-tune channel changed from Ch. 96 to Ch. 1998 nearly two weeks ago, I have disabled "Auto-tune to HD" on each box. Doing this has enabled the IR Blaster to send codes for a reduced set of three-digit maximum channel numbers. To achieve HD viewing with this device, my system has been designed to pass ReplayTV output to a video scaler which upconverts the signal to HD for display on a HDTV. It was indicated on another forum that fine-tuning parameters for the Explorer box were best modified by only adjusting the Minimum Digits To Send value in ReplayTV settings. I have changed this from "1" to "3" on the boxes and will monitor for auto-tune and report back in several days.

jole60 said:

Becky said:
@Jole60, are you able to test the changes that Mark suggested? Please let us know the results!

@Mark_K, thanks very much for the information you provided!

Becky, this is what I've done so far. Mark, your thoughtful insights are always helpful and appreciated. Regarding discussion of four-digit (HD) channel tuning, I have always removed HD channels ( Ch.1003+ on the box) from the ReplayTV program guide as soon as they appeared. This was done because ReplayTV is a SD device which cannot output a HD signal. Since the auto-tune channel changed from Ch. 96 to Ch. 1998 nearly two weeks ago, I have disabled "Auto-tune to HD" on each box. Doing this has enabled the IR Blaster to send codes for a reduced set of three-digit maximum channel numbers. To achieve HD viewing with this device, my system has been designed to pass ReplayTV output to a video scaler which upconverts the signal to HD for display on a HDTV. It was indicated on another forum that fine-tuning parameters for the Explorer box were best modified by only adjusting the Minimum Digits To Send value in ReplayTV settings. I have changed this from "1" to "3" on the boxes and will monitor for auto-tune and report back in several days.

All boxes continue to auto-tune to Ch. 1998. Mark, you indicated that adjusting the IR timing delay might resolve the problem. Any recommended change to these defaults will be greatly appreciated. Inter-action delay: 200 ms Response delay: 0 ms Pre-command delay: 0 ms Inter-command delay: 200 ms

I've seen tuning errors during this scenerio:

Replay is tuned to a 4 digit channel

Replay wakes up and sends the current channel (4 digits) over IR to the cable box.

While the cable box tunes the above, the replay switches to a new channel (to record a new show) and sends a new channel over IR.

This interferes with the original IR command.

The pre-command delay solves the above...  Set this delay longer than the total time to send 4 digits + enter (if used)

You can reproduce the problem by quickly changing channels on the replaytv. (e.g. pressing chan+, chan-, chan+, chan- when on a 4 digit channel).  Watch the digits that the replaytv sends the cable box.

BTW, this is never a problem with the replayTV controlling a minibox..  Probably because I never need it to tune 4 digit channels.