Digest for sci.electronics.repair@googlegroups.com - 5 updates in 3 topics

9:40 AM Penedão 0 comments
bitrex <user@example.net>: Aug 25 11:26AM -0400

Is there a suitable modern replacement for the ua208a TO-99 can-type
op amp as used in e.g. the HP oven oscillators, that's available and
doesn't cost an arm and a leg?
 
<https://datasheetspdf.com/pdf/1305470/Fairchild/UA208A/1>
 
Probably less expensive to just buy another module, maybe
ehsjr <ehsjr@verizon.net>: Aug 24 06:44PM -0400

On 8/23/2022 10:24 PM, bob prohaska wrote:
 
You want a precision that is doomed by the technique you
intend to use - stacking cells. Instead, build a voltage
reference using a single IC: ADR01 available from Digikey
https://www.digikey.com/en/products/detail/analog-devices-inc/ADR01AUJZ-REEL7/996117
It provides 10V output at +/- point one percent (.1%)
 
Calibrate your meters to that.
 
Ed
amdx <amdx@knology.net>: Aug 25 05:29AM -0500

On 8/23/2022 9:24 PM, bob prohaska wrote:
> CR2032 cells are readily available, but voltage details are scarce.
 
> Thanks for reading,
 
> bob prohaska
 
Aliexpress, Ebay and Amazon have some for under $10, and more for under $20.
 
David Farber <farberbear.unspam@aol.com>: Aug 24 05:34PM -0700

On 8/21/2022 9:28 PM, Phil Allison wrote:
 
> ** Read my first post again.
 
> SCRs, once triggered, conduct large currents with small voltage drops.
 
> ..... Phil
 
Finally got around to testing the SCR and it works perfectly. The only
other active components other than the power supply diodes are the two
IC's, LM2901 and LM2903.
 
Thanks for your reply.
 
--
David Farber
Los Osos, CA
Phil Allison <pallison49@gmail.com>: Aug 24 07:00PM -0700

David Farber wrote:
 
> > ** Read my first post again.
 
> > SCRs, once triggered, conduct large currents with small voltage drops.
 
> Finally got around to testing the SCR and it works perfectly.
 
** Yep - expected that.
 
The only
> other active components other than the power supply diodes are the two
> IC's, LM2901 and LM2903.
 
** I see a TO92 pak transistor near the SCR.
Lotta resistors about too.
Dead easy to check them for opens.
 
.... Phil
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Digest for sci.electronics.repair@googlegroups.com - 7 updates in 1 topic

9:40 AM Penedão 0 comments
David Farber <farberbear.unspam@aol.com>: Aug 19 07:39PM -0700

This Schumacher 1042A-PE battery charger stopped functioning today. It
seemed to work for a little while but when I noticed the car battery's
voltage wasn't slowly increasing after performing a 2 amp charge for 2
hours, I checked the voltage at the charger's cables and it was 0 volts.
The continuity of the switches and cables were all good. I did find a
power semiconductor which I could not identify, BTW70-200SN. I looked in
an old ECG cross-reference book and the closest match was for a
BTW69-800 which is an SCR in a TO-218 package. The package seems to
match the device I'm looking for. I made some measurements with my
Simpson 464 DVM on the 2k ohm scale. Pins 1 and 3 measure 38 ohms
regardless of test lead polarity. All other combinations of continuity
measure open circuit. In circuit, pins 1 and 2 are soldered together.
Any idea what this component is or how to test it?
 
Thanks for your reply.
 
David Farber
Los Osos, CA
Phil Allison <pallison49@gmail.com>: Aug 19 09:08PM -0700

David Farber wrote:
=============
 
> regardless of test lead polarity. All other combinations of continuity
> measure open circuit. In circuit, pins 1 and 2 are soldered together.
> Any idea what this component is or how to test it?
 
** Could be an SCR maybe.............
 
With a 1A, current limited, DC supply of about 12 V, + on the anode - on the cathode, apply a brief pulse of +50mA at +1.5V to the gate with - on the cathode as well. The 12 volt supply should the be clamped at about +1.2V.
You 38 ohm readings are normal.
 
 
..... Phil
Jeff Liebermann <jeffl@cruzio.com>: Aug 19 10:25PM -0700

On Fri, 19 Aug 2022 19:39:03 -0700, David Farber
 
>This Schumacher 1042A-PE battery charger...
 
Are you sure about that model number? Methinks that SE-1052A-PE is
more likely.
 
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
David Farber <farberbear.unspam@aol.com>: Aug 19 11:30PM -0700

On 8/19/2022 10:25 PM, Jeff Liebermann wrote:
 
>> This Schumacher 1042A-PE battery charger...
 
> Are you sure about that model number? Methinks that SE-1052A-PE is
> more likely.
 
Youthinks correctly! It is a 1052A.
 
Thanks for your reply.
--
David Farber
Los Osos, CA
Jeff Liebermann <jeffl@cruzio.com>: Aug 20 12:09AM -0700

On Fri, 19 Aug 2022 23:30:27 -0700, David Farber
 
>> Are you sure about that model number? Methinks that SE-1052A-PE is
>> more likely.
 
>Youthinks correctly! It is a 1052A.
 
Unfortunately, that didn't help when looking for information using
Google search. I couldn't find anything on the SE-1052A-PE except the
owners manual. No schematics or articles on repairing it. No photos
of the inside.
<http://powertool.manualsonline.com/manuals/mfg/schumacher/se_1012d_se_1052.html>
Notice that the user manual covers a range of models which probably
share similar circuitry. Try searching for the other models.
SE-1010-2, SE-1012D, SE-1052, SE-1250
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Jeff Liebermann <jeffl@cruzio.com>: Aug 20 12:28AM -0700

On Sat, 20 Aug 2022 00:09:28 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
 
>Notice that the user manual covers a range of models which probably
>share similar circuitry. Try searching for the other models.
>SE-1010-2, SE-1012D, SE-1052, SE-1250
 
Bingo, except that there's no SCR in the schematic.
<https://www.fixya.com/support/t25414948-wiring_diagram_switch_se_1052>
<https://www.fixya.com/support/t7882270-looking_wirring_diagram>
Kinda looks like just the PCB wiring and not the complete unit. This
is from a different charger (SE-1275A) that MIGHT have the same
wiring. How close are the drawing and schematic to what you have?
 
 
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
David Farber <farberbear.unspam@aol.com>: Aug 20 08:38AM -0700

On 8/19/2022 9:08 PM, Phil Allison wrote:
 
> ..... Phil
 
Hi Phil,
 
Looks like I have to make another correction. Jeff pointed out the model
number I posted was wrong, the correct model is 1052A-PE
 
The other correction is that pins 1 and 2 of the "SCR" are NOT soldered
together on the pc board. Pin 2 (center pin) is snipped off and the
connection is made through the component's heat sink. This is the same
heat sink which is electrically common to one end of four discreet
(bridge?) diodes.
 
Getting back to the testing of the SCR (if it is an SCR), how do I
identify anode, cathode, and gate?
 
Thanks for your reply.
--
David Farber
Los Osos, CA
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Digest for sci.electronics.repair@googlegroups.com - 1 update in 1 topic

9:40 AM Penedão 0 comments
vjp2.at@at.BioStrategist.dot.dot.com: Aug 02 06:24PM

Many thanks to both replies.
 
I was leading to the conclusion that BLU shuts off USB OTG, for which I
needed to root. I switched on developer mode and the bootlogger switch. But
KingoRoot refused to root on grounds of 0x17ae78 error, and RootEssentials
showed no vold.fsab in etc, only a volte-cfg.xml.
 
I don't get to choose maufacturer or carrier, so am stuck with this BLU C5L
with Android 11 running on a reseller of T-mobile. My Prior phone was an
LG423 running on what appeared to be a GSM reseller of CDM Verizon.
 
--
Vasos Panagiotopoulos panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
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