Fixing inaccurate wall clock

This cheap wall clock cost me ~$3. After few weeks it showed up that it is quite inaccurate being late ~40 seconds per week. While these plastic cogs tend to wear after few years causing clock to even stuck completely in some position it was unlikely that this kind of defect was present from the start.

Crystal resonator used in this clock had no markings and I think it may be production recoil. After changing it to another similar size crystal decent accuracy of the clock was restored.

Further testing showed that with new crystal clock is slightly speeding, so 20pF trimmer was added for adjustment.

Review: Patriot Rage 16 GB

Popular fast, "quad channel" USB pendrive.

 There seems to be serial number engraved on USB plug.

Advertised speed: 27/25 MB/s (R/W).

Real speed is little disappointing:

On second PC I'm getting write speed close to 17 MB/s - still not matching advertised.

USB descriptors:

Device Descriptor:

------------------------------

Value Valuename

0x12 bLength

0x01 bDescriptorType

0x0200 bcdUSB

0x00 bDeviceClass   

0x00 bDeviceSubClass   

0x00 bDeviceProtocol   

0x40 bMaxPacketSize0   (64 Bytes)

0x13FE idVendor

0x3800 idProduct

0x0100 bcdDevice

0x01 iManufacturer   (        )

0x02 iProduct   (Patriot Memory)

0x03 iSerialNumber   (0701281B2F1D5128)

0x01 bNumConfigurations

Hex dump: 

0x12 0x01 0x00 0x02 0x00 0x00 0x00 0x40 0xFE 0x13 

0x00 0x38 0x00 0x01 0x01 0x02 0x03 0x01 

Device Qualifier Descriptor:

------------------------------

Value Valuename

0x0A bLength

0x06 bDescriptorType

0x0200 bcdUSB

0x00 bDeviceClass   

0x00 bDeviceSubClass   

0x00 bDeviceProtocol   

0x40 bMaxPacketSize0   (64 Bytes)

0x01 bNumConfigurations 

0x00 bReserved 

Hex dump: 

0x0A 0x06 0x00 0x02 0x00 0x00 0x00 0x40 0x01 0x00 

Configuration Descriptor:

------------------------------

Value Valuename

0x09 bLength

0x02 bDescriptorType

0x0020 wTotalLength

0x01 bNumInterfaces

0x01 bConfigurationValue

0x00 iConfiguration

0x80 bmAttributes   (Bus-powered Device)

0x96 MaxPower   (300 mA)

Hex dump: 

0x09 0x02 0x20 0x00 0x01 0x01 0x00 0x80 0x96 

Interface Descriptor:

------------------------------

Value Valuename

0x09 bLength

0x04 bDescriptorType

0x00 bInterfaceNumber

0x00 bAlternateSetting

0x02 bNumEndPoints

0x08 bInterfaceClass   (Mass Storage Device Class)

0x06 bInterfaceSubClass   (Transparent SCSI subclass)

0x50 bInterfaceProtocol   (Bulk only transport)

0x00 iInterface

Hex dump: 

0x09 0x04 0x00 0x00 0x02 0x08 0x06 0x50 0x00 

Endpoint Descriptor:

------------------------------

Value Valuename

0x07 bLength

0x05 bDescriptorType

0x81 bEndpointAddress   (In-Endpoint)

0x02 bmAttributes

   Transfer Type:           Bulk-Transfer

   Synchronization Type:    None

   Usage Type:              Data

0x0200 wMaxPacketSize   (512 Bytes) 

0x00 bInterval

Hex dump: 

0x07 0x05 0x81 0x02 0x00 0x02 0x00 

Endpoint Descriptor:

------------------------------

Value Valuename

0x07 bLength

0x05 bDescriptorType

0x02 bEndpointAddress   (Out-Endpoint)

0x02 bmAttributes

   Transfer Type:           Bulk-Transfer

   Synchronization Type:    None

   Usage Type:              Data

0x0200 wMaxPacketSize   (512 Bytes) 

0x00 bInterval

Hex dump: 

0x07 0x05 0x02 0x02 0x00 0x02 0x00 

Other Speed Configuration Descriptor:

------------------------------

Value Valuename

0x09 bLength

0x07 bDescriptorType

0x0020 wTotalLength

0x01 bNumInterfaces

0x01 bConfigurationValue

0x00 iConfiguration

0x80 bmAttributes   (Bus-powered Device)

0x96 MaxPower   (300 mA)

Hex dump: 

0x09 0x07 0x20 0x00 0x01 0x01 0x00 0x80 0x96 

Interface Descriptor:

------------------------------

Value Valuename

0x09 bLength

0x04 bDescriptorType

0x00 bInterfaceNumber

0x00 bAlternateSetting

0x02 bNumEndPoints

0x08 bInterfaceClass   (Mass Storage Device Class)

0x06 bInterfaceSubClass   (Transparent SCSI subclass)

0x50 bInterfaceProtocol   (Bulk only transport)

0x00 iInterface

Hex dump: 

0x09 0x04 0x00 0x00 0x02 0x08 0x06 0x50 0x00 

Endpoint Descriptor:

------------------------------

Value Valuename

0x07 bLength

0x05 bDescriptorType

0x81 bEndpointAddress   (In-Endpoint)

0x02 bmAttributes

   Transfer Type:           Bulk-Transfer

   Synchronization Type:    None

   Usage Type:              Data

0x0040 wMaxPacketSize   (64 Bytes) 

0x00 bInterval

Hex dump: 

0x07 0x05 0x81 0x02 0x40 0x00 0x00 

Endpoint Descriptor:

------------------------------

Value Valuename

0x07 bLength

0x05 bDescriptorType

0x02 bEndpointAddress   (Out-Endpoint)

0x02 bmAttributes

   Transfer Type:           Bulk-Transfer

   Synchronization Type:    None

   Usage Type:              Data

0x0040 wMaxPacketSize   (64 Bytes) 

0x00 bInterval

Hex dump: 

0x07 0x05 0x02 0x02 0x40 0x00 0x00 

Whole Device Descriptor as hex dump: 

0x12, 0x01, 0x00, 0x02, 0x00, 0x00, 0x00, 0x40, 0xFE, 0x13, 

0x00, 0x38, 0x00, 0x01, 0x01, 0x02, 0x03, 0x01

Whole Device Qualifier Descriptor as hex dump: 

0x0A, 0x06, 0x00, 0x02, 0x00, 0x00, 0x00, 0x40, 0x01, 0x00

Whole Configuration Descriptor as hex dump: 

0x09, 0x02, 0x20, 0x00, 0x01, 0x01, 0x00, 0x80, 0x96, 0x09, 

0x04, 0x00, 0x00, 0x02, 0x08, 0x06, 0x50, 0x00, 0x07, 0x05, 

0x81, 0x02, 0x00, 0x02, 0x00, 0x07, 0x05, 0x02, 0x02, 0x00, 

0x02, 0x00

Whole Other Speed Configuration Descriptor as hex dump: 

0x09, 0x07, 0x20, 0x00, 0x01, 0x01, 0x00, 0x80, 0x96, 0x09, 

0x04, 0x00, 0x00, 0x02, 0x08, 0x06, 0x50, 0x00, 0x07, 0x05, 

0x81, 0x02, 0x40, 0x00, 0x00, 0x07, 0x05, 0x02, 0x02, 0x40, 

0x00, 0x00

The funny thing is I've tested similar (same model, same capacity) pendrive before and it's speed matched advertised. I can't blame formatting here as using Patriot Performance Formatting tool doesn't make much of a difference.

Tests conducted by others also show great variation in speed: nirsoft.net Patriot Rage tests.