WordPress Excerpts

Thank you for answer. Ive checked the link you posted but still doesnt work. The posts have thumbnails,  add_theme_support( 'post-thumbnails' ) is included in functions.php. My php files are:
Category.php

<?php
/**
 *
 * archive.php
 *
 * The archive template. Used when a category, author, or date is queried.
 * Note that this template will be overridden by category.php, author.php, and date.php for their respective query types. 
 *
 * More detailed information about template’s hierarchy: http://codex.wordpress.org/Template_Hierarchy
 *
 */
get_header(); ?>
			<?php get_sidebar('top'); ?>
			<?php
			if (have_posts()) {
				global $posts;
				$post = $posts[0];
				theme_ob_start();

				if (is_category()) {
					echo '<h4>' . single_cat_title('', false) . '</h4>';
					echo category_description();
				} elseif (is_tag()) {
					echo '<h4>' . single_tag_title('', false) . '</h4>';
				} elseif (is_day()) {
					echo '<h4>' . sprintf(__('Daily Archives: <span>%s</span>', THEME_NS), get_the_date()) . '</h4>';
				} elseif (is_month()) {
					echo '<h4>' . sprintf(__('Monthly Archives: <span>%s</span>', THEME_NS), get_the_date('F Y')) . '</h4>';
				} elseif (is_year()) {
					echo '<h4>' . sprintf(__('Yearly Archives: <span>%s</span>', THEME_NS), get_the_date('Y')) . '</h4>';
				} elseif (is_author()) {
					the_post();
					echo theme_get_avatar(array('id' => get_the_author_meta('user_email')));
					echo '<h4>' . get_the_author() . '</h4>';
					$desc = get_the_author_meta('description');
					if ($desc) {
						echo '<div class="author-description">' . $desc . '</div>';
					}
					rewind_posts();
				} elseif (isset($_GET['paged']) && !empty($_GET['paged'])) {
					echo '<h4>' . __('Blog Archives', THEME_NS) . '</h4>';
				}
				theme_post_wrapper(array('content' => theme_ob_get_clean(), 'class' => 'breadcrumbs'));

				/* Display navigation to next/previous pages when applicable */
				if (theme_get_option('theme_top_posts_navigation')) {
					theme_page_navigation();
				}

				/* Start the Loop */
				while (have_posts()) {
					the_post();
                                       
					get_template_part('content', 'excerpt');
				}

				/* Display navigation to next/previous pages when applicable */
				if (theme_get_option('theme_bottom_posts_navigation')) {
					theme_page_navigation();
				}
			} else {
				theme_404_content();
			}
			?>
			<?php get_sidebar('bottom'); ?>
<?php get_footer();

Select all Open in new window

content-excerpt.php

<?php
/**
 *
 * content*.php
 *
 * The post format template. You can change the structure of your posts or add/remove post elements here.
 * 
 * 'id' - post id
 * 'class' - post class
 * 'thumbnail' - post icon
 * 'title' - post title
 * 'before' - post header metadata
 * 'content' - post content
 * 'after' - post footer metadata
 * 
 * To create a new custom post format template you must create a file "content-YourTemplateName.php"
 * Then copy the contents of the existing content.php into your file and edit it the way you want.
 * 
 * Change an existing get_template_part() function as follows:
 * get_template_part('content', 'YourTemplateName');
 *
 */

global $post;
theme_post_wrapper(
		array(
			'id' => theme_get_post_id(),
			'class' => theme_get_post_class(),
                        'thumbnail' => theme_get_post_thumbnail(),
                        
			'title' => '<a href="' . get_permalink($post->ID) . '" rel="bookmark" title="' . strip_tags(get_the_title()) . '">' . get_the_title() . '</a>',
			'heading' => theme_get_option('theme_' . (is_home() ? 'posts' : 'single') . '_article_title_tag'),
			'before' => theme_get_metadata_icons('date,author,edit', 'header'),
			'content' => theme_get_excerpt(array('auto' => true)),
                        'after' => theme_get_metadata_icons('category,tag,comments', 'footer')
		)
);

?>

Select all Open in new window

Ive tried many variants to include the_post_thumbnail() with no result.

Any idea where to look further on?
Thanks in advance.
Regards,
Raul M.

as  'Featured Image'